#include<stdio.h>
#include<stdlib.h>

int cmpfunc(const void*a,const void*b)
{
    float fa=*(float*)a;
    float fb=*(float*)b;
    if(fa<fb)return -1;
    if(fa>fb)return 1;
    return 0;
}
int main(){
    int N, M;
    scanf("%d",&N);
    scanf("%d",&M);
    if(N<=0||M<=0)
    {
        printf("Invalid Input\n");
        return 0;
        float arr[N];
        for(int i=0;i<N;i++)
        {
            for(int j=0;j<M;j++)
            {
                float temp;
                scanf("%f",&temp);
                if(j==0)arr[i]=temp;
            }
        }
        qsort(arr,N,sizeof(float),cmpfunc);
        float median;
        if(N%2==1)
        {
            median=arr[n/2];
        }
        else
        {
            median=(arr[(n-1)/2]+arr[n/2]/2.0);
        }
        printf("%.2f\n",median);
    }
}