#include<stdio.h>

int main()
{
	unsigned long n,v[1000000],i,j,a,x,s,e;
	freopen("elmaj.in","r",stdin);
	freopen("elmaj.out","w",stdout);
	scanf("%ld",&n);
	for(i=0;i<n;i++)
	scanf("%ld",&v[i]);
	for(i=0;i<n;i++)
	for(j=0;j<i;j++)
	if(v[j]>v[i]) 
	{a=v[i];v[i]=v[j];v[j]=a;}
	a=1;s=0;
	x=n/2+1;
	e=v[0];
	for(i=1;i<n;i++)
	if(v[i]==v[i-1])
		{a++;}
	else
	if(a>=x)
		{printf("%ld%ld",e,a);break;}
	else
	{s+=a;a=1;e=v[i];if(s>=x) {printf("%d",-1);break;}}
	return 0;

}