#include<cstdio>
#include<cstring>
#define N 10010
using namespace std;
int a[N],n,i,x;
int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        memset(a,0,sizeof(a));
        for(i=1;i<=n;i++)scanf("%d",&x),a[x]++;
        for(i=1;i<10000;i++)if(a[i]>(n/2))break;
        if(i>=10000)puts("-1");else printf("%d\n",i);
    }
}