#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n + 1); i++)
using ll = long long;
using P = pair<int, int>;
using Graph = vector<vector<int>>;
using mint = modint998244353;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n; cin >> n;
    vector<int> d(n);
    rep(i, n)cin >> d[i];
    sort(d.begin(), d.end());
    reverse(d.begin(), d.end());

    cout << d[0]-n << endl;
}