#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, prev, i, ans = 0, x, step = 1;
  cin >> n;
  cin >> prev;
  ans = prev;
  if (n == 1) {
    cout << ans;
    return 0;
  }
  for (i = 0; i < n - 1; i++) {
    step++;
    cin >> x;
    ans += (step * x) - step + 1;
  }
  cout << ans;
  return 0;
}
