#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long n = 0, i = 0, ans = 0;
  ans = 0;
  cin >> n;
  for (int j = 1; j <= n; j++) {
    cin >> i;
    if (j == 1)
      ans += i;
    else
      ans += (i + (j - 1) * (i - 1));
  }
  cout << ans;
  return 0;
}
