#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
const double esp = 1e-10;
int n;
int main() {
  long long ans = 0;
  long long tmp;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    cin >> tmp;
    ans += (tmp - 1) * i;
  }
  cout << ans + n << endl;
  return 0;
}
