#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  long long a;
  while (scanf("%d", &n) == 1) {
    int i, j, k;
    long long ans = 0;
    for (i = 0; i < n; i++) {
      scanf("%I64d", &a);
      ans += (long long)(i) * (a - 1) + a;
    }
    printf("%I64d\n", ans);
  }
}
