#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001



int main(){
	
	int n;
	cin>>n;
	
	vector<int> cnt(100,0);
	rep(i,n){
		int a;
		cin>>a;
		cnt[a]++;
	}
	int ans = 0;
	rep(i,99){
		if(cnt[i]==0)ans += (i+1) * cnt[i+1];
	}
	
	cout<<ans<<endl;
	
	
	
	return 0;
}