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