#include <bits/stdc++.h>
using namespace std;
unsigned long long int n, a[1000], cnt, sol, x, y, dp[1000];
int main() {
  scanf("%I64d", &n);
  for (int i = 1; i <= n; i++) scanf("%I64d", &a[i]);
  dp[1] = a[1];
  for (int i = 2; i <= n; i++) {
    if (a[i] == 1) {
      dp[i] = dp[i - 1] + 1;
      continue;
    }
    dp[i] = ((i) * (a[i] - 1)) + dp[i - 1] + 1;
  }
  printf("%I64d \n", dp[n]);
  return 0;
}
