#include <bits/stdc++.h>
using namespace std;
long long num[1000];
int main() {
  int n, i, j, k;
  long long ans;
  while (cin >> n) {
    ans = 0;
    for (i = 1; i <= n; i++) cin >> num[i];
    for (i = 1; i <= n; i++) {
      ans += ((num[i] - 1) * (long long)(i - 1) + num[i]);
    }
    cout << ans << endl;
  }
}
