#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
  int n;
  cin >> n;
  vector <int> b(n);
  for (int i = 0; i < n; i++) {
	  cin >> b[i];
	}
  vector <int> c;
  for (int i = 0; i < n; i++) {
	  for (int j = 0; j < b[i]; j++) {
		  c.push_back(i);
		}
	}
  ll ans = 0;
  for (int i = 0; i < n; i++) {
	  ans += abs(c[i] - i);
	}
  cout << ans << endl;
  return 0;
}