we believe that our ability to increase the number of customers on our platform is an indicator of our market penetration , the growth of our business , and our potential future business opportunities . increasing awareness of our platform and capabilities , coupled with the mainstream adoption of cloud technology , has expanded the diversity of our customer base to include organizations of all sizes across all industries . over time , larger customers have constituted a greater share of our revenue , which has contributed to an increase in average revenue per customer . the number of customers who have greater than $ 100,000 in annual contract value with us was 691 , 443 and 255 as of january 31 , 2018 , 2017 and 2016 , respectively . we expect this trend to continue as larger enterprises recognize the value of our platform and replace their legacy iam infrastructure . we define a customer as a separate and distinct buying entity , such as a company , an educational or government institution , or a distinct business unit of a large company that has an active contract with us or one of our partners to access our platform . dollar-based retention rate our ability to generate revenue is dependent upon our ability to maintain our relationships with our customers and to increase their utilization of our platform . we believe we can achieve these goals by focusing on delivering value and functionality that enables us to both retain our existing customers and expand the number of users and products used within an existing customer . we assess our performance in this area by measuring our dollar-based retention rate . our dollar-based retention rate measures our ability to increase revenue across our existing customer base through expansion of users and products associated with a customer as offset by churn and contraction in the number of users and or products associated with a customer . our dollar-based retention rate is based upon our annual contract value , or acv , which is calculated based on the terms of that customer 's contract and represents the total contracted annual subscription amount as of that period end . we calculate our dollar-based retention rate as of a period end by starting with the acv from all customers as of twelve months prior to such period end , or prior period acv . we then calculate the acv from these same customers as of the current period end , or current period acv . current period acv includes any upsells and is net of contraction or churn over the trailing twelve months but excludes revenue from new customers in the current period . we then divide the total current period acv by the total prior period acv to arrive at our dollar-based retention rate . our dollar-based retention rate has consistently exceeded 120 % , which is primarily attributable to an expansion of users and up-selling additional products within our existing customers . larger enterprises often implement a limited initial deployment of our platform before increasing their deployment on a broader scale . calculated billings calculated billings represent our total revenue plus the change in deferred revenue in the period . calculated billings in any particular period reflects sales to new customers plus subscription renewals and upsells to existing 47 customers , and represent amounts invoiced for subscription , support and professional services . we typically invoice customers in advance in annual installments for subscriptions to our platform . calculated billings increased 62 % in the year ended january 31 , 2018 over the year ended january 31 , 2017 . as our calculated billings continue to grow in absolute terms , we expect our calculated billings growth rate to trend down over time . see the section titled “ selected consolidated financial data and other data—non-gaap financial measures ” for additional information and a reconciliation of calculated billings to total revenue . components of results of operations revenue subscription revenue . subscription revenue primarily consists of fees for access to and usage of our cloud-based platform and related support . we generate subscription fees pursuant to noncancelable contracts with a weighted average duration of 2.4 years as of january 31 , 2018 . subscription revenue is driven primarily by the number of customers , the number of users per customer and the products used . we typically invoice customers in advance in annual installments for subscriptions to our platform . we recognize subscription revenue ratably over the term of the subscription period beginning on the date access to our platform is provided , provided all other revenue recognition criteria have been met . professional services and other . professional services revenue includes fees from assisting customers in implementing and optimizing the use of our products . these services include application configuration , system integration and training services . we generally invoice customers monthly as the work is performed for time and materials arrangements . we generally have standalone value for our professional services and recognize revenue for the estimated fair value as a separate unit of accounting as services are performed or for those fixed-fee contracts , upon completion of the services . overhead allocation and employee compensation costs we allocate shared costs , such as facilities ( including rent , utilities and depreciation on equipment shared by all departments ) , information technology costs , and recruiting costs to all departments based on headcount . as such , allocated shared costs are reflected in each cost of revenue and operating expense category . employee compensation costs include salaries , bonuses , benefits and stock-based compensation for each operating expense category and sales commissions for sales and marketing . cost of revenue and gross margin cost of subscription . cost of subscription primarily consists of expenses related to hosting our services and providing support . story_separator_special_tag the information for each of these quarters has been prepared on the same basis as the audited annual consolidated financial statements included elsewhere in this annual report on form 10-k and , in the opinion of management , includes all adjustments , which consist only of normal recurring adjustments , necessary for the fair presentation of the results of operations for these periods . this data should be read in conjunction with our audited consolidated financial statements and related notes included elsewhere in this annual report on form 10-k. these quarterly results are not necessarily indicative of our results of operations to be expected for any future period . replace_table_token_22_th _ ( 1 ) amounts include stock-based compensation expense as follows : replace_table_token_23_th 57 replace_table_token_24_th quarterly revenue trends our quarterly revenue increased sequentially in each of the periods presented due primarily to increases in the number of new customers as well as expansion within existing customers and sales of new products . we have typically acquired more new customers in the fourth quarter of our fiscal year , though this seasonality is sometimes not immediately apparent in our revenue due to the fact that we recognize subscription revenue over the term of the contract . our contracts have a weighted-average duration of 2.4 years . beginning in the three months ended april 30 , 2016 , we began to see the impact of migrating more of the pricing for our professional services engagements to a time and materials basis . with this change , the impact of fixed fee project completions on professional services revenue was less significant in recent periods and we do not expect a material impact in future periods . quarterly cost of revenue and gross margin trends our quarterly gross margin has generally been increasing due to increasing subscription revenue and related economies of scale combined with the overall growth in our professional services revenue and increased utilization of professional services personnel . quarterly operating expense trends total costs and expenses generally increased sequentially for the fiscal quarters presented , primarily due to the addition of personnel in connection with the expansion of our business . our research and development expenses can fluctuate quarter to quarter based on the timing and extent of capitalizable internal-use software development activities . sales and marketing expenses grew sequentially over the periods . sales and marketing expenses included $ 5.0 million and $ 3.3 million of expenses related to our annual customer conference in the third quarter of fiscal 2018 and 2017 , respectively . our sales and marketing expenses generally increase in the quarter in which the conference is held . general and administrative costs generally increased in recent quarters due to higher outside professional service fees in connection with preparing to be and operating as a public company . 58 non-gaap financial measures in addition to our results determined in accordance with u.s. generally accepted accounting principles , or gaap , we believe the following non-gaap measures are useful in evaluating our operating performance . we use the below referenced non-gaap financial information , collectively , to evaluate our ongoing operations and for internal planning and forecasting purposes . we believe that non-gaap financial information , when taken collectively , may be helpful to investors because it provides consistency and comparability with past financial performance , and assists in comparisons with other companies , some of which use similar non-gaap financial information to supplement their gaap results . the non-gaap financial information is presented for supplemental informational purposes only , and should not be considered a substitute for financial information presented in accordance with gaap , and may be different from similarly-titled non-gaap measures used by other companies . a reconciliation is provided below for each non-gaap financial measure to the most directly comparable financial measure stated in accordance with gaap . investors are encouraged to review the related gaap financial measures and the reconciliation of these non-gaap financial measures to their most directly comparable gaap financial measures . non-gaap gross profit and non-gaap gross margin we define non-gaap gross profit and non-gaap gross margin as gaap gross profit and gaap gross margin , adjusted for stock-based compensation expense and amortization of acquired intangibles . replace_table_token_25_th non-gaap operating loss and non-gaap operating margin we define non-gaap operating loss and non-gaap operating margin as gaap operating loss and gaap operating margin , adjusted for stock-based compensation expense , charitable contributions , amortization of acquired intangibles and acquisition related compensation expense . replace_table_token_26_th 59 free cash flow we define free cash flow as net cash used in operating activities , less cash used for purchases of property and equipment and capitalized internal-use software costs . replace_table_token_27_th calculated billings we define calculated billings as total revenue plus the change in deferred revenue during the period . replace_table_token_28_th liquidity and capital resources as of january 31 , 2018 , our principal sources of liquidity were cash , cash equivalents and short-term investments totaling $ 229.7 million , which were held for working capital purposes , as well as the available balance of our credit facility , described further below . our cash equivalents and investments were comprised primarily of money market funds , u.s. treasury securities , commercial paper and corporate debt securities . we have generated significant operating losses and negative cash flows from operations as reflected in our accumulated deficit and consolidated statements of cash flows . we expect to continue to incur operating losses and negative cash flows from operations for the foreseeable future . 60 in april 2017 , upon completion of our initial public offering , or ipo , we received aggregate proceeds of $ 200.0 million , net of underwriters ' discounts and commissions , before deducting offering costs of approximately $ 5.6 million . historically , we have financed our operations primarily through the net proceeds we received through private sales of equity securities , as well as payments received from customers for subscription and

cash flows the following table summarizes our cash flows for the periods indicated : replace_table_token_29_th operating activities our largest source of operating cash is cash collections from our customers for subscription and professional services . our primary uses of cash from operating activities are for employee-related expenditures , marketing expenses and third-party hosting costs . historically , we have generated negative cash flows from operating activities and have 61 supplemented working capital requirements through net proceeds from the private sale of equity securities and in the current period from the net proceeds of our ipo . during the year ended january 31 , 2018 , cash used in operating activities was $ 25.2 million primarily due to our net loss of $ 114.4 million , adjusted for non-cash charges of $ 76.5 million and net cash inflows of $ 12.7 million provided by changes in our operating assets and liabilities . non-cash charges primarily consisted of stock-based compensation , amortization of deferred commissions , depreciation and amortization of property and equipment and intangible assets , write-off of capitalized internal-use software costs , deferred income taxes and charitable contributions . the primary drivers of the changes in operating assets and liabilities related to a $ 54.9 million increase in deferred revenue , and an increase of $ 7.6 million in accounts payable , accrued compensation and accrued other expenses , offsetby an increase of $ 18.3 million in accounts receivable , a $ 21.4 million increase in deferred commissions and an increase of $ 10.1 million in prepaid expenses and other assets .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```cash flows the following table summarizes our cash flows for the periods indicated : replace_table_token_29_th operating activities our largest source of operating cash is cash collections from our customers for subscription and professional services . our primary uses of cash from operating activities are for employee-related expenditures , marketing expenses and third-party hosting costs . historically , we have generated negative cash flows from operating activities and have 61 supplemented working capital requirements through net proceeds from the private sale of equity securities and in the current period from the net proceeds of our ipo . during the year ended january 31 , 2018 , cash used in operating activities was $ 25.2 million primarily due to our net loss of $ 114.4 million , adjusted for non-cash charges of $ 76.5 million and net cash inflows of $ 12.7 million provided by changes in our operating assets and liabilities . non-cash charges primarily consisted of stock-based compensation , amortization of deferred commissions , depreciation and amortization of property and equipment and intangible assets , write-off of capitalized internal-use software costs , deferred income taxes and charitable contributions . the primary drivers of the changes in operating assets and liabilities related to a $ 54.9 million increase in deferred revenue , and an increase of $ 7.6 million in accounts payable , accrued compensation and accrued other expenses , offsetby an increase of $ 18.3 million in accounts receivable , a $ 21.4 million increase in deferred commissions and an increase of $ 10.1 million in prepaid expenses and other assets .
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 Suspicious Activity Report : we believe that our ability to increase the number of customers on our platform is an indicator of our market penetration , the growth of our business , and our potential future business opportunities . increasing awareness of our platform and capabilities , coupled with the mainstream adoption of cloud technology , has expanded the diversity of our customer base to include organizations of all sizes across all industries . over time , larger customers have constituted a greater share of our revenue , which has contributed to an increase in average revenue per customer . the number of customers who have greater than $ 100,000 in annual contract value with us was 691 , 443 and 255 as of january 31 , 2018 , 2017 and 2016 , respectively . we expect this trend to continue as larger enterprises recognize the value of our platform and replace their legacy iam infrastructure . we define a customer as a separate and distinct buying entity , such as a company , an educational or government institution , or a distinct business unit of a large company that has an active contract with us or one of our partners to access our platform . dollar-based retention rate our ability to generate revenue is dependent upon our ability to maintain our relationships with our customers and to increase their utilization of our platform . we believe we can achieve these goals by focusing on delivering value and functionality that enables us to both retain our existing customers and expand the number of users and products used within an existing customer . we assess our performance in this area by measuring our dollar-based retention rate . our dollar-based retention rate measures our ability to increase revenue across our existing customer base through expansion of users and products associated with a customer as offset by churn and contraction in the number of users and or products associated with a customer . our dollar-based retention rate is based upon our annual contract value , or acv , which is calculated based on the terms of that customer 's contract and represents the total contracted annual subscription amount as of that period end . we calculate our dollar-based retention rate as of a period end by starting with the acv from all customers as of twelve months prior to such period end , or prior period acv . we then calculate the acv from these same customers as of the current period end , or current period acv . current period acv includes any upsells and is net of contraction or churn over the trailing twelve months but excludes revenue from new customers in the current period . we then divide the total current period acv by the total prior period acv to arrive at our dollar-based retention rate . our dollar-based retention rate has consistently exceeded 120 % , which is primarily attributable to an expansion of users and up-selling additional products within our existing customers . larger enterprises often implement a limited initial deployment of our platform before increasing their deployment on a broader scale . calculated billings calculated billings represent our total revenue plus the change in deferred revenue in the period . calculated billings in any particular period reflects sales to new customers plus subscription renewals and upsells to existing 47 customers , and represent amounts invoiced for subscription , support and professional services . we typically invoice customers in advance in annual installments for subscriptions to our platform . calculated billings increased 62 % in the year ended january 31 , 2018 over the year ended january 31 , 2017 . as our calculated billings continue to grow in absolute terms , we expect our calculated billings growth rate to trend down over time . see the section titled “ selected consolidated financial data and other data—non-gaap financial measures ” for additional information and a reconciliation of calculated billings to total revenue . components of results of operations revenue subscription revenue . subscription revenue primarily consists of fees for access to and usage of our cloud-based platform and related support . we generate subscription fees pursuant to noncancelable contracts with a weighted average duration of 2.4 years as of january 31 , 2018 . subscription revenue is driven primarily by the number of customers , the number of users per customer and the products used . we typically invoice customers in advance in annual installments for subscriptions to our platform . we recognize subscription revenue ratably over the term of the subscription period beginning on the date access to our platform is provided , provided all other revenue recognition criteria have been met . professional services and other . professional services revenue includes fees from assisting customers in implementing and optimizing the use of our products . these services include application configuration , system integration and training services . we generally invoice customers monthly as the work is performed for time and materials arrangements . we generally have standalone value for our professional services and recognize revenue for the estimated fair value as a separate unit of accounting as services are performed or for those fixed-fee contracts , upon completion of the services . overhead allocation and employee compensation costs we allocate shared costs , such as facilities ( including rent , utilities and depreciation on equipment shared by all departments ) , information technology costs , and recruiting costs to all departments based on headcount . as such , allocated shared costs are reflected in each cost of revenue and operating expense category . employee compensation costs include salaries , bonuses , benefits and stock-based compensation for each operating expense category and sales commissions for sales and marketing . cost of revenue and gross margin cost of subscription . cost of subscription primarily consists of expenses related to hosting our services and providing support . story_separator_special_tag the information for each of these quarters has been prepared on the same basis as the audited annual consolidated financial statements included elsewhere in this annual report on form 10-k and , in the opinion of management , includes all adjustments , which consist only of normal recurring adjustments , necessary for the fair presentation of the results of operations for these periods . this data should be read in conjunction with our audited consolidated financial statements and related notes included elsewhere in this annual report on form 10-k. these quarterly results are not necessarily indicative of our results of operations to be expected for any future period . replace_table_token_22_th _ ( 1 ) amounts include stock-based compensation expense as follows : replace_table_token_23_th 57 replace_table_token_24_th quarterly revenue trends our quarterly revenue increased sequentially in each of the periods presented due primarily to increases in the number of new customers as well as expansion within existing customers and sales of new products . we have typically acquired more new customers in the fourth quarter of our fiscal year , though this seasonality is sometimes not immediately apparent in our revenue due to the fact that we recognize subscription revenue over the term of the contract . our contracts have a weighted-average duration of 2.4 years . beginning in the three months ended april 30 , 2016 , we began to see the impact of migrating more of the pricing for our professional services engagements to a time and materials basis . with this change , the impact of fixed fee project completions on professional services revenue was less significant in recent periods and we do not expect a material impact in future periods . quarterly cost of revenue and gross margin trends our quarterly gross margin has generally been increasing due to increasing subscription revenue and related economies of scale combined with the overall growth in our professional services revenue and increased utilization of professional services personnel . quarterly operating expense trends total costs and expenses generally increased sequentially for the fiscal quarters presented , primarily due to the addition of personnel in connection with the expansion of our business . our research and development expenses can fluctuate quarter to quarter based on the timing and extent of capitalizable internal-use software development activities . sales and marketing expenses grew sequentially over the periods . sales and marketing expenses included $ 5.0 million and $ 3.3 million of expenses related to our annual customer conference in the third quarter of fiscal 2018 and 2017 , respectively . our sales and marketing expenses generally increase in the quarter in which the conference is held . general and administrative costs generally increased in recent quarters due to higher outside professional service fees in connection with preparing to be and operating as a public company . 58 non-gaap financial measures in addition to our results determined in accordance with u.s. generally accepted accounting principles , or gaap , we believe the following non-gaap measures are useful in evaluating our operating performance . we use the below referenced non-gaap financial information , collectively , to evaluate our ongoing operations and for internal planning and forecasting purposes . we believe that non-gaap financial information , when taken collectively , may be helpful to investors because it provides consistency and comparability with past financial performance , and assists in comparisons with other companies , some of which use similar non-gaap financial information to supplement their gaap results . the non-gaap financial information is presented for supplemental informational purposes only , and should not be considered a substitute for financial information presented in accordance with gaap , and may be different from similarly-titled non-gaap measures used by other companies . a reconciliation is provided below for each non-gaap financial measure to the most directly comparable financial measure stated in accordance with gaap . investors are encouraged to review the related gaap financial measures and the reconciliation of these non-gaap financial measures to their most directly comparable gaap financial measures . non-gaap gross profit and non-gaap gross margin we define non-gaap gross profit and non-gaap gross margin as gaap gross profit and gaap gross margin , adjusted for stock-based compensation expense and amortization of acquired intangibles . replace_table_token_25_th non-gaap operating loss and non-gaap operating margin we define non-gaap operating loss and non-gaap operating margin as gaap operating loss and gaap operating margin , adjusted for stock-based compensation expense , charitable contributions , amortization of acquired intangibles and acquisition related compensation expense . replace_table_token_26_th 59 free cash flow we define free cash flow as net cash used in operating activities , less cash used for purchases of property and equipment and capitalized internal-use software costs . replace_table_token_27_th calculated billings we define calculated billings as total revenue plus the change in deferred revenue during the period . replace_table_token_28_th liquidity and capital resources as of january 31 , 2018 , our principal sources of liquidity were cash , cash equivalents and short-term investments totaling $ 229.7 million , which were held for working capital purposes , as well as the available balance of our credit facility , described further below . our cash equivalents and investments were comprised primarily of money market funds , u.s. treasury securities , commercial paper and corporate debt securities . we have generated significant operating losses and negative cash flows from operations as reflected in our accumulated deficit and consolidated statements of cash flows . we expect to continue to incur operating losses and negative cash flows from operations for the foreseeable future . 60 in april 2017 , upon completion of our initial public offering , or ipo , we received aggregate proceeds of $ 200.0 million , net of underwriters ' discounts and commissions , before deducting offering costs of approximately $ 5.6 million . historically , we have financed our operations primarily through the net proceeds we received through private sales of equity securities , as well as payments received from customers for subscription and

