#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  long long int a[n], i, sum = 0;
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < n; i++) {
    if (a[i] >= 2)
      sum = sum + i * (a[i] - 1) + a[i];
    else
      sum = sum + a[i];
  }
  cout << sum;
}
