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