#include <bits/stdc++.h>
using namespace std;
const int maxint = -1u >> 1;
const double pi = acos(-1.0);
long long tmp;
int n;
int main() {
  while (cin >> n) {
    long long cnt = 0LL;
    long long ans = 0LL;
    for (int i = 0; i < n; i++) {
      cin >> tmp;
      ans += tmp;
      ans += (tmp - 1LL) * cnt;
      cnt++;
    }
    cout << ans << endl;
  }
  return 0;
}
