#include <bits/stdc++.h>
using namespace std;
signed main() {
//freopen("input.txt", "r", stdin);
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
int a[n];
for(int i = 0; i < n; i++) {
cin >> a[i];
}
sort(a, a + n, greater<int>());
unique(a, a + n);
cout << a[1] % a[0] << endl;
return 0;
}
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