#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int a[100000], n, s = 0, i, j = 0;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (i = 0; i < n; i++) {
    s = s + ((a[i] - 1) * (i + 1));
  }
  s = s + n;
  cout << s;
  return 0;
}
