# ifndef ONLINE_JUDGE
# define _GLIBCXX_DEBUG
# endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
# define rep(i, n) for(int i = 0; i < (int)(n); ++i)
# define all(v) v.begin(), v.end()

int main(){
  constexpr char endl = '\n';
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  //input();
  int N;cin >> N;
  vi P(N);
  for(auto &&e : P)  cin >> e;
  //solve();
  int score = 0;
  rep(i, N){
    if(P[i] == N)  score -= i+1;
    else  score += i+1;
  }
  //output();
  if(score < 0)  cout << 0 << endl;
  else  cout << score << endl;
}