#include <bits/stdc++.h>
using namespace std;
const int maxn = -1;
const int INF = 99999999;
int main() {
  long long ans = 0;
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    long long x;
    cin >> x;
    ans += i * (x - 1) + 1;
  }
  cout << ans << endl;
  return 0;
}
