#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <iostream>
#include <string>
#include <set>
#include <map>
#include <vector>
#include <queue>
#define ll long long
#define db double
using namespace std;
const ll N = 1e5 + 100;
ll tt,n,mx;
void solve() {
	scanf("%lld",&n);
	mx = -1;
	for (ll i = 1;i <= n;i++) {
		ll x;
		scanf("%lld",&x);
		mx = max(mx,x);
	}
	printf("%lld",mx - n);
}
int main() {
	tt = 1;
	while(tt) {
		solve();
		tt--;
	}
	return 0;
}