#include <iostream>
using namespace std;
typedef long long ll;

int main() {
  int n; cin >> n; ll b[n];
  for(int i=0; i<n; i++) cin >> b[i];
  ll nw = 0, nw_cost = 0;
  for(int i=0; i<n; i++) {
    nw += b[i] - 1;
    nw_cost += abs(nw);
  }
  cout << nw_cost << endl;
}