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