#include <bits/stdc++.h>
using namespace std;
const double pi = 3.14159265359;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  long long x, cnt = 0, i;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> x;
    cnt += x + ((i - 1) * (x - 1));
  }
  cout << cnt;
  return 0;
}
