#include <cstdio>
#include <algorithm>
using namespace std;
int v[3000005];
int main(){
	freopen("sdo.in","r",stdin);
	freopen("sdo.out","w",stdout);
	int n,i,cont=0;
	scanf("%d %d",&n);
	for(i=1;i<=n;++i)
		scanf("%d",&v[i]);
	nth_element(v+1,v+n/2,v+n+1);
	for(i=1;i<=n;++i)
		if(v[i]=v[n/2])
			++cont;
	if(cont>n/2){
		printf("%d",v[n/2])
		return 0;
	}
	printf("-1");
}