The average miner Vaganych took refresher courses. As soon as a miner completes the courses, he should take exams. The hardest one is a computer test called "Testing Pants for Sadness".

The test consists of n questions; the questions are to be answered strictly in the order in which they are given, from question 1 to question n. Question i contains ai answer variants, exactly one of them is correct. 

A click is regarded as selecting any answer in any question. The goal is to select the correct answer for each of the n questions. If Vaganych selects a wrong answer for some question, then all selected answers become unselected and the test starts from the very beginning, from question 1 again. But Vaganych remembers everything. The order of answers for each question and the order of questions remain unchanged, as well as the question and answers themselves.

Vaganych is very smart and his memory is superb, yet he is unbelievably unlucky and knows nothing whatsoever about the test's theme. How many clicks will he have to perform in the worst case?

Input

The first line contains a positive integer n (1 ≤ n ≤ 100). It is the number of questions in the test. The second line contains space-separated n positive integers ai (1 ≤ ai ≤ 109), the number of answer variants to question i.

Output

Print a single number — the minimal number of clicks needed to pass the test it the worst-case scenario. 

Please do not use the %lld specificator to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specificator.

Examples

Input

2
1 1


Output

2

Input

2
2 2


Output

5

Input

1
10


Output

10

Note

Note to the second sample. In the worst-case scenario you will need five clicks: 

  * the first click selects the first variant to the first question, this answer turns out to be wrong. 
  * the second click selects the second variant to the first question, it proves correct and we move on to the second question; 
  * the third click selects the first variant to the second question, it is wrong and we go back to question 1; 
  * the fourth click selects the second variant to the first question, it proves as correct as it was and we move on to the second question; 
  * the fifth click selects the second variant to the second question, it proves correct, the test is finished. 

import java.awt.List;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map.Entry;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;
import java.util.Stack;
import java.util.*;


 
 
public class cool {

	private static InputStream stream;
	private static PrintWriter pw;
	
	
	
//	static int a;
//	static int b;
//	static int f = 0;
	static int n;
	static int m;
//	static int[][] arr;
	//static char[][] arr;
	
	static int Arr[];
	static int tree[];
	
	static int time = 0;
	
	static int[][] dir = {{-1,0},{0,1},{1,0},{0,-1}};

	static int visited[];
	static int visited2[][];
	static Stack<Integer> stack;
	
//	static ArrayList<Integer> ans;

//	static int arr[][];
//	static int arr[];
	static char[][] arr;
	static char[][] ans;
//	static int[][] visited;
//  static int c;
//	static int d[];
//	static int arr[][];
	static ArrayList[] adj;
//	static ArrayList<Integer> ans;
//	static int f;
	static int red[];
	static int black[];
	static int color[];
//	static ArrayList<Integer> comp[];

	static int f = 0;
	static int k = 0;
	static int count = 0;
	static int total = 0;
	static int ini[];
	
	static ArrayList<Node> list;
	static ArrayList<Integer> ind;


	
	public static void main(String[] args){
		//InputReader(System.in);
		pw = new PrintWriter(System.out);
		
		Scanner in = new Scanner(System.in);

		int a = in.nextInt();
		in.nextLine();
		
		long ans = 0;
		
		for(int i = 0;i<a;i++){
			long c = in.nextLong();
			ans += c + (c-1)*i;
		}
		
		pw.println(ans);
		pw.close();
	}
	
	
	public static void dfs(int i){
		
		if(visited[i] == 1)
			return;
		
		if(color[i] == 1){
			return;
		}
		
		visited[i] = 1;
		//System.out.println(i);
	
		for(int j = 0;j<adj[i].size();j++){
			
			Node p = (Node)adj[i].get(j);
			
			if(color[p.a-1] == 0){
				dfs(p.a-1);
			}else{
				count = 0;
				total = p.b;
				bfs(p.a-1);
				
				red[i] += total;
				black[i] += count;
			}
			
			
		}
		
	}
	
	
	public static long ansf(int i){
    	
		if(color[i] == 1)
			return 0;
		
		if(visited[i] == 1){
			return 0;
		}
		
		visited[i] = 1;
		for(int j = 0;j<adj[i].size();j++){
			Node p = (Node)adj[i].get(j);
			
			if(color[p.a-1] == 0 && visited[p.a-1] == 0){
				red[i] += ansf(p.a-1) + p.b*black[p.a-1]+ red[p.a-1];
				black[i] += black[p.a - 1];
			}
		
		}
		//System.out.println(red[i] + " reurn;");
		return red[i];
	
    	
    }
	
	
	public static void bfs(int i){
		if(visited[i] == 1){
			return;
		}
		if(color[i] == 0){
			return;
		}
		visited[i] = 1;
		count++;
		
		
		//System.out.println(i);
		for(int j = 0;j<adj[i].size();j++){
			
			Node p = (Node)adj[i].get(j);
			
			if(color[p.a-1] == 1 && visited[p.a-1] == 0){
				//System.out.println(p.b + " l");
				total += p.b;
				bfs(p.a-1);
			}
		}
		
	}
	
	
	public static long pow(long n,long p){
        long  result = 1;
         if(p==0)
           return 1;
       if (p==1)
           return n;
       while(p!=0)
       {
           if(p%2==1)
               result *= n;
//           if(result>=m)
//           result%=m;
           p >>=1;
           n*=n;
//           if(n>=m)
//           n%=m;
       }
       return result;
       }
	

	
	public static int cs(ArrayList<Integer> arr, int low, int high, int x)
	{
	  int mid;    
	 
	  if(x <= arr.get(low))
	    return low; 
	 
	  if(x > arr.get(high))
	    return -1;  
	 
	 
	  mid = (low + high)/2; 
	 
	  if(arr.get(mid) == x)
	    return mid;
	    
	  else if(arr.get(mid) < x)
	  {
	    if(mid + 1 <= high && x <= arr.get(mid+1))
	      return mid + 1;
	    else
	      return cs(arr, mid+1, high, x);
	  }
	   
	  else
	  {
	    if(mid - 1 >= low && x > arr.get(mid-1))
	      return mid;
	    else    
	      return cs(arr, low, mid - 1, x);
	  }
	}
	
	
	public static int fs(int arr[], int low, int high, int x)
	{
	   
	    if (low > high)
	        return -1;
	 
	    if (x >= arr[high])
	        return high;
	 
	    // Find the middle point
	    int mid = (low+high)/2;
	 
	    // If middle point is floor.
	    if (arr[mid] == x)
	        return mid;
	 
	    // If x lies between mid-1 and mid
	    if (mid > 0 && arr[mid-1] <= x && x < arr[mid])
	        return mid-1;
	 
	    // If x is smaller than mid, floor must be in
	    // left half.
	    if (x < arr[mid])
	        return fs(arr, low, mid-1, x);
	 
	    // If mid-1 is not floor and x is greater than
	    // arr[mid],
	    return fs(arr, mid+1, high, x);
	}
	 

	public static long gcd(long x, long y) {
		if (x == 0)
			return y;
		else
			return gcd( y % x,x);
	}
	
//	public static void dfs(int a,int p){
//		System.out.println(a);
//		if(a > 30000){
//			return;
//		}
//		
//		if(visited[a] == 1){
//			return;
//		}
//		
//		visited[a] = 1;
//		
//		if(ini[a] != 0){
//			count+= ini[a];
//		}
//		
//		int l = a-p;
//		
//		if(visited[a+l-1] == 0){
//			dfs(a+l-1,a);
//		}else if(visited[a+l] == 0){
//			dfs(a+l,a);
//		}else if(visited[a+l+1] == 0){
//			dfs(a+l+1,a);
//		}
//		
//	}
//	
	
	
	
	
	
	public static int prev(int i,boolean[] arr){
		
		while(arr[i]){
			if(i == 0){
				if(arr[i]){
					return -1;
				}else{
					return 0;
				}
				
				
			}
			
			
			i--;
			
		}
		
		return i;
		
		
	}
	
	
	public static int next(int i,boolean[] arr){
		
		
		while(arr[i]){
			if(i == arr.length-1){
				if(arr[i]){
					return -1;
				}else{
					return 0;
				}
			}
			
			i++;
		}
		
		
		return i;
	}
	

	
	private static Map<String, Integer> sortByValue(Map<String, Integer> unsortMap) {

        // 1. Convert Map to List of Map
        LinkedList<Entry<String, Integer>> list =
                new LinkedList<Map.Entry<String, Integer>>(unsortMap.entrySet());

        // 2. Sort list with Collections.sort(), provide a custom Comparator
        //    Try switch the o1 o2 position for a different order
        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> o1,
                               Map.Entry<String, Integer> o2) {
                return (o1.getValue()).compareTo(o2.getValue());
            }
        });

        // 3. Loop the sorted list and put it into a new insertion order Map LinkedHashMap
        Map<String, Integer> sortedMap = new LinkedHashMap<String, Integer>();
        for (Map.Entry<String, Integer> entry : list) {
            sortedMap.put(entry.getKey(), entry.getValue());
        }

        /*
        //classic iterator example
        for (Iterator<Map.Entry<String, Integer>> it = list.iterator(); it.hasNext(); ) {
            Map.Entry<String, Integer> entry = it.next();
            sortedMap.put(entry.getKey(), entry.getValue());
        }*/


        return sortedMap;
    }

	
	public static ArrayList<Integer> Range(int[] numbers, int target) {
	  

	    int low = 0, high = numbers.length - 1;
	    // get the start index of target number
	    int startIndex = -1;
	    while (low <= high) {
	        int mid = (high - low) / 2 + low;
	        if (numbers[mid] > target) {
	            high = mid - 1;
	        } else if (numbers[mid] == target) {
	            startIndex = mid;
	            high = mid - 1;
	        } else
	            low = mid + 1;
	    }

	    // get the end index of target number
	    int endIndex = -1;
	    low = 0;
	    high = numbers.length - 1;
	    while (low <= high) {
	        int mid = (high - low) / 2 + low;
	        if (numbers[mid] > target) {
	            high = mid - 1;
	        } else if (numbers[mid] == target) {
	            endIndex = mid;
	            low = mid + 1;
	        } else
	            low = mid + 1;
	    }

	    ArrayList<Integer> list = new ArrayList<Integer>();
	    int c = 0;
	    if (startIndex != -1 && endIndex != -1){
	        for(int i = startIndex;i<=endIndex;i++){
	        	list.add(i);
	        }
	    }
	    
	    
	    return list;
	    
	    
	}

	
	
	 private static int root(int Arr[],int i)
	    {
	        while(Arr[ i ] != i)           //chase parent of current element until it reaches root
	        {
	            Arr[ i ] = Arr[ Arr[ i ] ] ; 
	            i = Arr[ i ];
	        }
	        return i;
	    }
	 
	 private static void union(int Arr[],int size[],int A,int B)
	    {
	        int root_A = root(Arr,A);
	        int root_B = root(Arr,B);
	     
	       System.out.println(root_A + " " + root_B);
	        if(root_A != root_B){
	        	 if(size[root_A] < size[root_B ])
	 	        {
	        		 Arr[ root_A ] = Arr[root_B];
	        		 size[root_B] += size[root_A];	 	
	 	        }
	 	        else
	 	        {   	
	 	        	Arr[ root_B ] = Arr[root_A];
	 	        	size[root_A] += size[root_B];	 	   
	 	        }	
	        }
	    }
	 
	 private static boolean find(int A,int B)
	    {
	        if( root(Arr,A)==root(Arr,B) )       //if A and B have the same root, it means that they are connected.
	        return true;
	        else
	        return false;
	    }
	 
	
	


//	
//	public static void bfs(int i){
//		
//		Queue<Integer> q=new LinkedList<Integer>();
//    	q.add(i);
//    	
//    	visited[i] = 1;
//    	c++;
//    	nodes++;
//    	while(!q.isEmpty()){
//    		int top=q.poll();
//    		
//    		Iterator<Integer> it= arr[top].listIterator();
//    		while(it.hasNext()){
//    			int next =it.next();
//    			
//    			if(visited[next] == 0){
//    				nodes++;
//    				visited[next] = 1;
//    				q.add(next);
//    			}
//    		
//    		}
//    	}
//		
//	}
	
	
	
//	public static void dfs(int i){
//		
//		
//		if(visited[i] == 1){
//			return;
//		}
//		
//		visited[i] = 1;
//		con[c].add(i);
//		//System.out.print(i + " ");
//		for(int j = 0;j<arr[i].size();j++){
//			dfs(arr[i].get(j));
//		}
//		
//	}
//	
//	
//	public static void dfss(int i){
//		if(visited[i] == 1){
//			return;
//		}
//		
//		visited[i] = 1;
//		
//		for(int j = 0;j<arr[i].size();j++){
//			dfss(arr[i].get(j));
//		}
//	//	System.out.println(i);
//		stack.push(i);
//	}
//	
//	public static void reverse(){
//		ArrayList[] temp = new ArrayList[n];
//		
//		for(int i = 0;i<n;i++){
//			temp[i] = new ArrayList();
//		}
//		
//		for(int i = 0;i<n;i++){
//			for(int j = 0;j<arr[i].size();j++){
//				temp[arr[i].get(j)].add(i);
//			}
//		}
//		
//		arr = temp;
//		
//	}
//	
//	
	
	
	
	
	
	
	public static boolean isPrime(int n) {
		// Corner cases
		if (n <= 1)
			return false;
		if (n <= 3)
			return true;
 
		// This is checked so that we can skip 
		// middle five numbers in below loop
		if (n % 2 == 0 || n % 3 == 0)
			return false;
 
		for (int i = 5; i * i <= n; i = i + 6)
			if (n % i == 0 || n % (i + 2) == 0)
				return false;
 
		return true;
	}
	
		 
	 // union code starts	
	
	
	 
	 // union code ends
	
	
	 
//	 // Segment tree code begins
//	 
//	 
//	 static void build(int node,int start,int end)
//	 {
//	 if(start==end)
//	 tree[node]=a[start];
//	 else
//	 {
//	 int mid=(start+end)/2;
//	 build(2*node,start,mid);
//	 build(2*node+1,mid+1,end);
//	 if(tree[2*node]<tree[2*node+1])
//	 tree[node]=tree[2*node];
//	 else
//	 tree[node]=tree[2*node+1];
//	 }
//	 }
//	 
//	 
//	 static void update(int node,int start,int end,int idx,int val)
//	 {
//	 if(start==end)
//	 {
//	 a[idx]=val;
//	 tree[node]=val;
//	 }
//	 else
//	 {
//	 int mid=(start+end)/2;
//	 if(idx>=start&&idx<=mid)
//	 update(2*node,start,mid,idx,val);
//	 else
//	 update(2*node+1,mid+1,end,idx,val);
//	 if(tree[2*node]<tree[2*node+1])
//	 tree[node]=tree[2*node];
//	 else
//	 tree[node]=tree[2*node+1];
//	 }
//	 }
//	 
//	 static int query(int node,int start,int end,int l,int r)
//	 {
//	 if(l>end||start>r)
//	 return 100005;
//	 if(l<=start&&r>=end)
//	 return tree[node];
//	 int p1,p2;
//	 int mid=(start+end)/2;
//	 p1=query(2*node,start,mid,l,r);
//	 p2=query(2*node+1,mid+1,end,l,r);
//	 if(p1<p2)
//	 return p1;
//	 else
//	 return p2;
//	 }
//	 
//	 
//	 
//}

}

class Stone implements Comparable<Stone>{
	
	int a;
	int b;
	int c;
	int i;
	
	Stone(int a,int b,int c,int d){
		this.a = a;
		this.b = b;
		this.c = c;
		this.i = d;
	}

	@Override
	public int compareTo(Stone b) {

		if(this.c > b.c){
			return 1;
		}else if(this.c < b.c){
			return -1;
		}else if(this.b > b.b){
			return 1;
		}else if(this.b < b.b){
			return -1;
		}else if(this.a > b.a){
			return 1;
		}else if(this.a < b.a){
			return -1;
		}
		
		return 0;
	}
	

	
	
}


class Node{
	int a;
	int b;
}

class point{
	int a;
	int b;
}


class MyComp2 implements Comparator<Node>{
    
	@Override
	public int compare(Node o1, Node o2) {
		
		if( o1.b > o2.b){
			return 1;
		}else if( o1.b < o2.b){
			return -1;
		}else{
			if(o1.a == o2.a){
				return 0;
			}else if(o1.a > o2.a){
				return 1;
			}else if(o1.a < o2.a){
				return -1;
			}
		}
		
		return 0;
	}
}


class Card implements Comparable<Card>
{
	int a,b;
	public Card(int w,int h)
	{
		this.a=w;
		this.b=h;
		
	}
	public int compareTo(Card that)
	{
		return this.a-that.a;
	}
}
