#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin >> n;
  int sum = 0;
  long long res = 0;
  for (int i = 0; i < n; ++i) {
    int b;
    cin >> b;
    sum += b;
    res += abs(sum - (i + 1));
  }
  cout << res << '\n';
}