#include <bits/stdc++.h>
using namespace std;
int n;
long long ans, temp;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> temp;
    ans += temp;
    if (temp > 1) ans += (temp - 1) * ((long long)i - 1);
  }
  cout << ans << "\n";
  return 0;
}
