#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, k;
  long long tt, tmp;
  scanf("%d", &n);
  tt = n;
  for (i = 1; i <= n; i++) {
    scanf("%d", &k);
    tmp = k - 1;
    tmp *= i;
    tt += tmp;
  }
  cout << tt << endl;
  return 0;
}
