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