数据国税

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 7;

int n;
int a[MAXN];
int main(){
	scanf("%d",&n);
	for(int i = 1;i <= n;i++){
		scanf("%d",a + i);
	}
	sort(a + 1,a + n + 1);
	int i = n - 1;
	while(a[i] == a[n]){
		i--;
	}
	int mx = a[i];
	int ans = -1;
	for(;i >= 1;i--){
		if(a[i] != mx){
			ans = a[i];
			break;
		}
	}
	if(ans != -1){
		for(int j = 1;j <= n;j++){
			if(a[n] % a[j] > ans){
				ans = a[n] % a[j];
				break;
			}
		}
	}
	printf("%d",ans);
	return 0;
}

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