historically , we derived more than 61 % of our revenue in each of the last three fiscal years from sales of our mass notification application . our pricing model is based on the number of applications subscribed to and , per application , the number of people , locations and things connected to our platform as well as the volume of communications . we also offer premium services including data feeds for social media , threat intelligence and weather . we generate additional revenue by expanding the number of applications that our customers subscribe to and the number of contacts and devices connected to our platform . we generated revenue of $ 200.9 million in 2019 , $ 147.1 million in 2018 , $ 104.4 million in 2017 and $ 76.8 million in 2016 , representing year-over-year increases of 37 % in 2019 , 41 % in 2018 and 36 % in 2017. we had net losses of $ 52.3 million , $ 47.5 million , $ 19.6 million and $ 11.3 million in 2019 , 2018 , 2017 and 2016 , respectively . as of december 31 , 2019 , and 2018 , 23 % and 19 % of our customers , respectively , were located outside of the united states and these customers generated 22 % and 19 % of our total revenue for the years ended december 31 , 2019 and 2018 , respectively . 51 we have focused on rapidly growing our business and believe that the future growth of our business is dependent on many factors , including our ability to increase the functionality of our platform and applications , expand our customer base , accelerate adoption of our applications beyond mass notification within our existing customer base and expand our international presence . our future growth will also depend on the growth in the market for critical event management solutions and our ability to effectively compete . in order to further penetrate the market for critical event management solutions and capitalize on what we believe to be a significant opportunity , we intend to continue to invest in research and development , build-out our data center infrastructure and services capabilities and hire additional sales representatives , both domestically and internationally , to drive sales to new customers and incremental sales of new applications to existing customers . nevertheless , we expect to continue to incur losses in the near term and , if we are unable to achieve our growth objectives , we may not be able to achieve profitability . recent developments in april 2019 , we acquired all of the issued and outstanding shares of stock of missionmode solutions , inc. ( “ missionmode ” ) for base consideration of $ 6.8 million . there is also a potential contingent payment of up to $ 1.0 million that can be earned in addition to the base consideration by the sellers based on successfully converting missionmode 's customers to our products ; however , at december 31 , 2019 , it was determined to not be probable that missionmode would meet the threshold to convert missionmode 's customers to our products . our acquisition of missionmode was made primarily to expand our customer base and to a lesser extent to complement some of the existing facets of missionmode 's business with our existing customers . in july 2019 , we entered into a membership interest purchase agreement with nc4 inc. , nc4 public sector llc , and celerium group inc. , pursuant to which we purchased all of the issued and outstanding membership interest of nc4 inc. and nc4 public sector llc ( collectively , “ nc4 ” ) for total consideration of approximately $ 84.5 million . we paid approximately $ 51.7 million in cash at closing and paid the remaining purchase price with 320,998 newly issued shares of our common stock . on the date of this acquisition , the price of our common stock on the nasdaq global market was $ 102.18 per share . our acquisition of nc4 was made primarily to expand our customer base and to a lesser extent to complement some of the existing facets of nc4 's business with our existing products . in december 2019 , we issued $ 450 million aggregate principal amount of 0.125 % convertible senior notes due december 15 , 2024 ( the “ 2024 notes ” ) , including $ 75 million aggregate principal amount of 2024 notes issued upon exercise in full by the initial purchasers of their option to purchase additional 2024 notes . the 2024 notes will mature on december 15 , 2024 , unless earlier redeemed or repurchased by us or converted by the holder pursuant to their terms . in connection with the issuance of the 2024 notes , we entered into capped call transactions with certain counterparties affiliated with the initial purchasers and other financial institutions . the cost of the purchased capped calls was $ 44.9 million . the capped call transactions are expected to reduce potential dilution of earnings per share upon conversion of the 2024 notes . in connection with the issuance of the 2024 notes in december 2019 , we paid $ 57.8 million to repurchase $ 23.0 million in aggregate principal amount of our 1.50 % convertible senior notes due november 1 , 2022 ( the “ 2022 notes ” ) . we also partially terminated capped call options entered into in connection with the 2022 notes during fiscal year 2019 and received $ 5.8 million . on february 7 , 2020 , we entered into a stock purchase agreement with connexient , inc. ( “ connexient ” ) pursuant to which we purchased all of the issued and outstanding shares of stock of connexient for a base consideration of $ 20.5 million . story_separator_special_tag subscription cost and a $ 0.2 million increase in office related expenses to support the administrative team . 59 other expense , net replace_table_token_19_th other expense , net decreased by $ 4.3 million in 2018 compared to 2017 as a result of an increase in interest expense of $ 5.7 million related to interest expense due under our convertible senior notes . this increase was offset by an increase of $ 1.4 million of interest income earned on our short-term investments . income taxes replace_table_token_20_th income tax expense increased by $ 0.7 million in 2018 compared to 2017. the increase in taxes was primarily related to an increase in foreign taxes resulting from the acquisitions of ums and respond . other metrics we regularly monitor a number of financial and operating metrics including the following key metrics to evaluate our business , measure our performance , identify trends affecting our business , formulate business plans , and make strategic decisions . our other business metrics may be calculated in a manner different than similar other business metrics used by other companies ( in thousands ) : replace_table_token_21_th adjusted ebitda . adjusted ebitda represents our net loss before interest and investment income , net and interest expense , provision for income taxes , depreciation and amortization expense , loss on extinguishment of convertible notes and stock-based compensation expense . we do not consider these items to be indicative of our core operating performance . the items that are non-cash include depreciation and amortization expense and stock-based compensation expense . adjusted ebitda is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans , make strategic decisions regarding the allocation of capital and invest in initiatives that are focused on cultivating new markets for our solutions . in particular , the exclusion of certain expenses in calculating adjusted ebitda facilitates comparisons of our operating performance on a period-to-period basis . adjusted ebitda is not a measure calculated in accordance with gaap . we believe that adjusted ebitda provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , use of adjusted ebitda has limitations as an analytical tool , and you should not consider it in isolation or as a substitute for analysis of our financial results as reported under gaap . some of these limitations are : ( 1 ) although depreciation and amortization are non-cash charges , the capitalized software that is amortized will need to be replaced in the future , and adjusted ebitda does not reflect cash capital expenditure requirements for such replacements or for new capital expenditure requirements ; ( 2 ) adjusted ebitda does not reflect changes in , or cash requirements for , our working capital needs ; ( 3 ) adjusted ebitda does not reflect the potentially dilutive impact of 60 equity-based compensation ; ( 4 ) adjusted ebitda does not reflect tax payments or receipts that may represent a reduction or increase in cash available to us ; and ( 5 ) other companies , including companies in our industry , may calculate adjusted ebitda or similarly titled measures differently , which reduces the usefulness of the metric as a comparative measure . because of these and other limitations , you should consider adjusted ebitda alongside our other gaap-based financial performance measures , net loss and our other gaap financial results . the following table presents a reconciliation of adjusted ebitda to net loss , the most directly comparable gaap measure , for each of the periods indicated ( in thousands ) : replace_table_token_22_th adjusted gross margin . adjusted gross margin represents gross profit plus amortization of acquired intangibles and stock-based compensation . adjusted gross margin is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans . the exclusion of stock-based compensation expense and amortization of acquired intangibles facilitates comparisons of our operating performance on a period-to-period basis . in the near term , we expect these expenses to continue to negatively impact our gross profit . adjusted gross margin is not a measure calculated in accordance with gaap . we believe that adjusted gross margin provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , our use of adjusted gross margin has limitations as an analytical tool , and you should not consider it in isolation or as a substitute for analysis of our financial results as reported under gaap . you should consider adjusted gross margin alongside our other gaap-based financial performance measures , gross profit and our other gaap financial results . the following table presents a reconciliation of adjusted gross margin to gross profit , the most directly comparable gaap measure , for each of the periods indicated ( in thousands ) : replace_table_token_23_th 61 free cash flow . free cash flow represents net cash provided by operating activities minus capital expenditures and capitalized software development costs . free cash flow is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans . the exclusion of capital expenditures and amounts capitalized for internally-developed software facilitates comparisons of our operating performance on a period-to-period basis and excludes items that we do not consider to be indicative of our core operating performance . free cash flow is not a measure calculated in accordance with gaap . we believe that free cash flow provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , our use of free cash flow has limitations as an analytical tool , and you should not consider it in isolation or

cash received for the partial termination of the 2022 notes capped call options as well as a significant portion of the $ 139.1 million received in january 2019 as a result of our public offering of common stock . we have generated significant losses since inception and expect to continue to generate losses for the foreseeable futur e . we believe that our cash and cash equivalent balances and the cash flows generated by our operations will be sufficient to satisfy our anticipated cash needs for working capital and capital expenditures for at least the next 12 months . however , our belief may prove to be incorrect , and we could utilize our available financial resources sooner than we currently expect . our future capital requirements and the adequacy of available funds will depend on many factors , including those set forth in the section of this annual report on form 10-k titled “ risk factors. ” we can not assure you that we will be able to raise additional capital on acceptable terms or at all . in addition , if we fail to meet our operating plan during the next 12 months , our liquidity could be adversely affected . cash flows the following table summarizes our cash flows for the years ended december 31 , 2019 , 2018 and 2017 ( in thousands ) : replace_table_token_26_th at december 31 , 2019 , $ 6.7 million of the $ 539.7 million of cash , cash equivalents and restricted cash was held by foreign subsidiaries . our intention is to indefinitely reinvest foreign earnings in our foreign subsidiaries . if these earnings were used to fund domestic operations , they would be subject to additional income taxes upon repatriation . sources of funds follow-on public offering in january 2019 , we completed a follow-on public offering in which we sold 2,645,000 shares of our common stock , which included 345,000 shares sold pursuant to the exercise by the underwriters of an option to purchase additional shares , at a public offering price of $ 55.25 per share .


 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 received for the partial termination of the 2022 notes capped call options as well as a significant portion of the $ 139.1 million received in january 2019 as a result of our public offering of common stock . we have generated significant losses since inception and expect to continue to generate losses for the foreseeable futur e . we believe that our cash and cash equivalent balances and the cash flows generated by our operations will be sufficient to satisfy our anticipated cash needs for working capital and capital expenditures for at least the next 12 months . however , our belief may prove to be incorrect , and we could utilize our available financial resources sooner than we currently expect . our future capital requirements and the adequacy of available funds will depend on many factors , including those set forth in the section of this annual report on form 10-k titled “ risk factors. ” we can not assure you that we will be able to raise additional capital on acceptable terms or at all . in addition , if we fail to meet our operating plan during the next 12 months , our liquidity could be adversely affected . cash flows the following table summarizes our cash flows for the years ended december 31 , 2019 , 2018 and 2017 ( in thousands ) : replace_table_token_26_th at december 31 , 2019 , $ 6.7 million of the $ 539.7 million of cash , cash equivalents and restricted cash was held by foreign subsidiaries . our intention is to indefinitely reinvest foreign earnings in our foreign subsidiaries . if these earnings were used to fund domestic operations , they would be subject to additional income taxes upon repatriation . sources of funds follow-on public offering in january 2019 , we completed a follow-on public offering in which we sold 2,645,000 shares of our common stock , which included 345,000 shares sold pursuant to the exercise by the underwriters of an option to purchase additional shares , at a public offering price of $ 55.25 per share .
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 Suspicious Activity Report : historically , we derived more than 61 % of our revenue in each of the last three fiscal years from sales of our mass notification application . our pricing model is based on the number of applications subscribed to and , per application , the number of people , locations and things connected to our platform as well as the volume of communications . we also offer premium services including data feeds for social media , threat intelligence and weather . we generate additional revenue by expanding the number of applications that our customers subscribe to and the number of contacts and devices connected to our platform . we generated revenue of $ 200.9 million in 2019 , $ 147.1 million in 2018 , $ 104.4 million in 2017 and $ 76.8 million in 2016 , representing year-over-year increases of 37 % in 2019 , 41 % in 2018 and 36 % in 2017. we had net losses of $ 52.3 million , $ 47.5 million , $ 19.6 million and $ 11.3 million in 2019 , 2018 , 2017 and 2016 , respectively . as of december 31 , 2019 , and 2018 , 23 % and 19 % of our customers , respectively , were located outside of the united states and these customers generated 22 % and 19 % of our total revenue for the years ended december 31 , 2019 and 2018 , respectively . 51 we have focused on rapidly growing our business and believe that the future growth of our business is dependent on many factors , including our ability to increase the functionality of our platform and applications , expand our customer base , accelerate adoption of our applications beyond mass notification within our existing customer base and expand our international presence . our future growth will also depend on the growth in the market for critical event management solutions and our ability to effectively compete . in order to further penetrate the market for critical event management solutions and capitalize on what we believe to be a significant opportunity , we intend to continue to invest in research and development , build-out our data center infrastructure and services capabilities and hire additional sales representatives , both domestically and internationally , to drive sales to new customers and incremental sales of new applications to existing customers . nevertheless , we expect to continue to incur losses in the near term and , if we are unable to achieve our growth objectives , we may not be able to achieve profitability . recent developments in april 2019 , we acquired all of the issued and outstanding shares of stock of missionmode solutions , inc. ( “ missionmode ” ) for base consideration of $ 6.8 million . there is also a potential contingent payment of up to $ 1.0 million that can be earned in addition to the base consideration by the sellers based on successfully converting missionmode 's customers to our products ; however , at december 31 , 2019 , it was determined to not be probable that missionmode would meet the threshold to convert missionmode 's customers to our products . our acquisition of missionmode was made primarily to expand our customer base and to a lesser extent to complement some of the existing facets of missionmode 's business with our existing customers . in july 2019 , we entered into a membership interest purchase agreement with nc4 inc. , nc4 public sector llc , and celerium group inc. , pursuant to which we purchased all of the issued and outstanding membership interest of nc4 inc. and nc4 public sector llc ( collectively , “ nc4 ” ) for total consideration of approximately $ 84.5 million . we paid approximately $ 51.7 million in cash at closing and paid the remaining purchase price with 320,998 newly issued shares of our common stock . on the date of this acquisition , the price of our common stock on the nasdaq global market was $ 102.18 per share . our acquisition of nc4 was made primarily to expand our customer base and to a lesser extent to complement some of the existing facets of nc4 's business with our existing products . in december 2019 , we issued $ 450 million aggregate principal amount of 0.125 % convertible senior notes due december 15 , 2024 ( the “ 2024 notes ” ) , including $ 75 million aggregate principal amount of 2024 notes issued upon exercise in full by the initial purchasers of their option to purchase additional 2024 notes . the 2024 notes will mature on december 15 , 2024 , unless earlier redeemed or repurchased by us or converted by the holder pursuant to their terms . in connection with the issuance of the 2024 notes , we entered into capped call transactions with certain counterparties affiliated with the initial purchasers and other financial institutions . the cost of the purchased capped calls was $ 44.9 million . the capped call transactions are expected to reduce potential dilution of earnings per share upon conversion of the 2024 notes . in connection with the issuance of the 2024 notes in december 2019 , we paid $ 57.8 million to repurchase $ 23.0 million in aggregate principal amount of our 1.50 % convertible senior notes due november 1 , 2022 ( the “ 2022 notes ” ) . we also partially terminated capped call options entered into in connection with the 2022 notes during fiscal year 2019 and received $ 5.8 million . on february 7 , 2020 , we entered into a stock purchase agreement with connexient , inc. ( “ connexient ” ) pursuant to which we purchased all of the issued and outstanding shares of stock of connexient for a base consideration of $ 20.5 million . story_separator_special_tag subscription cost and a $ 0.2 million increase in office related expenses to support the administrative team . 59 other expense , net replace_table_token_19_th other expense , net decreased by $ 4.3 million in 2018 compared to 2017 as a result of an increase in interest expense of $ 5.7 million related to interest expense due under our convertible senior notes . this increase was offset by an increase of $ 1.4 million of interest income earned on our short-term investments . income taxes replace_table_token_20_th income tax expense increased by $ 0.7 million in 2018 compared to 2017. the increase in taxes was primarily related to an increase in foreign taxes resulting from the acquisitions of ums and respond . other metrics we regularly monitor a number of financial and operating metrics including the following key metrics to evaluate our business , measure our performance , identify trends affecting our business , formulate business plans , and make strategic decisions . our other business metrics may be calculated in a manner different than similar other business metrics used by other companies ( in thousands ) : replace_table_token_21_th adjusted ebitda . adjusted ebitda represents our net loss before interest and investment income , net and interest expense , provision for income taxes , depreciation and amortization expense , loss on extinguishment of convertible notes and stock-based compensation expense . we do not consider these items to be indicative of our core operating performance . the items that are non-cash include depreciation and amortization expense and stock-based compensation expense . adjusted ebitda is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans , make strategic decisions regarding the allocation of capital and invest in initiatives that are focused on cultivating new markets for our solutions . in particular , the exclusion of certain expenses in calculating adjusted ebitda facilitates comparisons of our operating performance on a period-to-period basis . adjusted ebitda is not a measure calculated in accordance with gaap . we believe that adjusted ebitda provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , use of adjusted ebitda has limitations as an analytical tool , and you should not consider it in isolation or as a substitute for analysis of our financial results as reported under gaap . some of these limitations are : ( 1 ) although depreciation and amortization are non-cash charges , the capitalized software that is amortized will need to be replaced in the future , and adjusted ebitda does not reflect cash capital expenditure requirements for such replacements or for new capital expenditure requirements ; ( 2 ) adjusted ebitda does not reflect changes in , or cash requirements for , our working capital needs ; ( 3 ) adjusted ebitda does not reflect the potentially dilutive impact of 60 equity-based compensation ; ( 4 ) adjusted ebitda does not reflect tax payments or receipts that may represent a reduction or increase in cash available to us ; and ( 5 ) other companies , including companies in our industry , may calculate adjusted ebitda or similarly titled measures differently , which reduces the usefulness of the metric as a comparative measure . because of these and other limitations , you should consider adjusted ebitda alongside our other gaap-based financial performance measures , net loss and our other gaap financial results . the following table presents a reconciliation of adjusted ebitda to net loss , the most directly comparable gaap measure , for each of the periods indicated ( in thousands ) : replace_table_token_22_th adjusted gross margin . adjusted gross margin represents gross profit plus amortization of acquired intangibles and stock-based compensation . adjusted gross margin is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans . the exclusion of stock-based compensation expense and amortization of acquired intangibles facilitates comparisons of our operating performance on a period-to-period basis . in the near term , we expect these expenses to continue to negatively impact our gross profit . adjusted gross margin is not a measure calculated in accordance with gaap . we believe that adjusted gross margin provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , our use of adjusted gross margin has limitations as an analytical tool , and you should not consider it in isolation or as a substitute for analysis of our financial results as reported under gaap . you should consider adjusted gross margin alongside our other gaap-based financial performance measures , gross profit and our other gaap financial results . the following table presents a reconciliation of adjusted gross margin to gross profit , the most directly comparable gaap measure , for each of the periods indicated ( in thousands ) : replace_table_token_23_th 61 free cash flow . free cash flow represents net cash provided by operating activities minus capital expenditures and capitalized software development costs . free cash flow is a measure used by management to understand and evaluate our core operating performance and trends and to generate future operating plans . the exclusion of capital expenditures and amounts capitalized for internally-developed software facilitates comparisons of our operating performance on a period-to-period basis and excludes items that we do not consider to be indicative of our core operating performance . free cash flow is not a measure calculated in accordance with gaap . we believe that free cash flow provides useful information to investors and others in understanding and evaluating our operating results in the same manner as our management and board of directors . nevertheless , our use of free cash flow has limitations as an analytical tool , and you should not consider it in isolation or

