#ifndef hari64
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#define debug(...)
#else
#include "util/viewer.hpp"
#define debug(...) viewer::_debug(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
using namespace std;
constexpr int INF = 1001001001;
constexpr long long INFll = 1001001001001001001;
template <class T>
bool chmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    return a > b ? a = b, 1 : 0;
}

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

    int N;
    cin >> N;
    vector<int> As(N);
    for (int i = 0; i < N; i++) {
        cin >> As[i];
    }

    cout << *max_element(As.begin(), As.end()) - N << endl;

    return 0;
}