#include <bits/stdc++.h>
using namespace std;
const int inf = 2000000000, mod = 1000000007;
const double eps = 0.000001;
int main() {
  long long n, s = 0;
  cin >> n;
  vector<long long> a(n);
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
    s += (i + 1) * (a[i] - 1);
  }
  cout << s + n;
  return 0;
}
