#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  vector<long long int> v1;
  long long int inp;
  long long int count1 = 0;
  for (long long int i = 0; i < n; i++) {
    cin >> inp;
    v1.push_back(inp);
    if (inp == 1) {
      count1++;
    }
  }
  long long int summing = 0;
  long long int pos1 = 0;
  long long int pos2 = v1.size() - 1;
  if (count1 == v1.size()) {
    cout << v1.size() << endl;
  } else {
    long long int times = 1;
    for (long long int i = pos1; i < v1.size(); i++) {
      summing = summing + (v1[i] - 1) * (i + 1);
      times++;
    }
    summing = summing + v1.size();
    cout << summing << endl;
  }
}
