#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int64_t> a;
  for (size_t i = 0; i < n; i++) {
    int64_t x;
    cin >> x;
    a.push_back(x);
  }
  int64_t sm = 0;
  int64_t c = 0;
  for (int i = a.size() - 1; i >= 0; i--) {
    c += a[i] + sm;
    sm += a[i] - 1;
  }
  cout << c;
  return 0;
}
