#include <bits/stdc++.h>
typedef long long i64;
using namespace std;
i64 n,i,j,maxi,maxk,smaxk;
set<i64> ls;
set<i64> rs,book;

int main() {
	scanf("%d",&n);
	for (i=0;i<n;i++) {
		scanf("%d",&j);
		if (ls.count(j))
			rs.insert(0);
		else
			ls.insert(j);
	}
	for (auto i:ls) {
		for (auto j:ls) {
			if (i==j) continue;
			rs.insert(i%j);
		}
	}
	maxk=-1;
	smaxk=-1;
	
	for (auto x:rs) {
		if (x>maxk) {
			smaxk=maxk;
			maxk=x;
		}
	}
	cout<<smaxk;
}

8 9 10 TLE 怎么办 求助