#include <iostream>
#include <cstdio>
#include <cstring>
#include <climits>
#include <algorithm>
using namespace std;

const int maxn=1000+10;
long int a[maxn],n,m,best,ans,p;
bool f;
int main()
{
	freopen ("leader.in","r",stdin);
	freopen ("leader.out","w",stdout);
	
	cin>>m>>n;
	for (int i=0; i<n; i++)
		cin>>a[i];
	sort(a,a+n);
	ans=1; best=n/2;
	for (int i=0; i<n; i++)
	{
		if (a[i]==a[i+1]) ans++;
		else 
		{
			if (ans>=best)
			{
				best=ans;p=a[i];f=1;
			}
			ans=1;
		}
	}
	if (f)	cout<<p<<endl;
	else cout<<-1<<endl;
	return 0;
}