#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, a[1000], i, cnt = 0;
  cin >> n;
  cnt = n;
  for (i = 0; i < n; i++) {
    cin >> a[i];
    cnt = cnt + (1 + i) * (a[i] - 1);
  }
  cout << cnt;
  return 0;
}
