#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
	int n,cnt=0;
	cin >> n;
	vector<int> a(n);
	for(int i=0;i<n;i++)	cin >> a[i];
	sort(a.begin(),a.end());
	for(int i=1;i<n;i++){
		while(a[i-1]>=a[i]){
			a[i]++;
			cnt++;
		}
	}
	cout << cnt << endl;
}