#include <bits/stdc++.h>
using namespace std;
long long d[1000], x, n;
vector<long long> a;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x;
    a.push_back(x);
  }
  d[0] = a[0];
  for (int i = 1; i < n; i++) {
    d[i] = d[i - 1] + (a[i] - 1) * (i + 1) + 1;
  }
  cout << d[n - 1];
  return 0;
}
