#include <bits/stdc++.h>
using namespace std;
const int MAX = 5e5 + 10, mod = 1e9 + 9, base = 41, INF = 1e9 + 10, sq = 502;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  long long n;
  cin >> n;
  long long ans = 0;
  for (long long i = 0; i < (n); ++i) {
    long long a;
    cin >> a;
    ans++;
    a--;
    ans += a * (1 + i);
  }
  cout << ans << endl;
  return 0;
}
