#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
using namespace std;
const int maxm=10005;
int n,m,a[maxm],sum,maxn=-1,temp;
int read()
{
	int x=0;
	char ch;
	ch=getchar();
	while(ch<'0'||ch>'9')
		ch=getchar();
	while(ch>='0'&&ch<='9')
	{
		x=x*10+ch-'0';
		ch=getchar();
	}
	return x;
}
int main()
{
	freopen("leader.in","r",stdin);
	freopen("leader.out","w",stdout);
	n=read();m=read();
	for(int i=1;i<=m;i++)
		a[i]=read();
	//printf("%d\n",(m>>1)+1);
	for(int i=1;i<=((m>>1)+1);i++)
	{
	//	printf("ok");
		if(a[i]!=0)
		{
			sum=1;
	//		printf("ok");
			for(int j=i+1;j<=m;j++)
			{
				if(a[i]==a[j])
				{
					sum++;
					a[j]=0;
				}
			}
			if(sum>maxn)
			{
				maxn=sum;
				temp=a[i];
			}	
		}
	}
	if(maxn>(m>>1))
		printf("%d",temp);
	else
		printf("-1");
	return 0;
}

/*
7 4
7 7 2 7 

7
*/