极简代码

#include<bits/stdc++.h>
long long n,z,a[1000005];
int main() {
	scanf("%d",&n);
	for(int i=1; i<=n; i++)scanf("%d",&a[i]);
	std::sort(a+1,a+n+1);
	z=std::unique(a+1,a+n+1)-a;
	if(z<=2)printf("-1");
	else printf("%d",(a[z-3]==3?a[z-3]+1:a[z-3]));
	return 0;
}