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

int main() {
  ios::sync_with_stdio(false);

  int N;
  cin >> N;

  vector<int> A(N);
  for (int i = 0; i < N; ++i) cin >> A[i];

  vector<int> pa(N + 1);
  for (int i = 0; i < N; ++i) pa[i + 1] = pa[i] + A[i];

  int64_t ans = 0;
  for (int i = 1; i < N; ++i) ans += abs(pa[i] - i);
  cout << ans << endl;

  return 0;
}