#include <bits/stdc++.h>
using namespace std;
bool btest = 0;
const int maxn = 1001;
const int INF = (int)1e9;
int n, m;
long long a[maxn];
int main() {
  ios::sync_with_stdio(0);
  cin >> n;
  long long ans = 0;
  for (long long i = 1; i <= n; i++) {
    cin >> a[(int)i];
    ans += (a[i] - 1) * i;
  }
  ans += n;
  cout << ans << endl;
  return 0;
}
