#include<iostream>
using namespace std;
int main()
{
    int m,n;
    cin>>m>>n;
    if(m<0 || n<0)
    {
        cout<<"Invalid input";
        return 0;
    }
    float l[m],o[n];
    float k[m+n]={};
    for(int i=0;i<m;i++)
    {
        cin>>l[i];
        if(l[i]<=0)
        {
            cout<<"Invalid input";
            return 0;
        }
        k[i]=l[i];
    }
    for(int j=0;j<n;j++)
    {
        cin>>o[j];
         if(o[j]<=0)
        {
            cout<<"Invalid input";
            return 0;
        }
        k[n+j]=o[j];
    }
    int total=m+n;
    sort(a,a=total);
    if(total%2==0)
    {
        float median =(k[total/2 -1] = k[total/2]) / 2.0;
        cout<<median;
    }
    else
    {
        cout<<k[total/2];
    }
   return 0;
}