#include <bits/stdc++.h>
using namespace std;
int main() {
  long long q[101];
  long long n, a, b, c;
  b = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> q[i];
    b = ((q[i] - 1) * (i + 1)) + 1 + b;
  }
  cout << b;
}
