#include <stdio.h>
int main(){
    int M,K;
    if (scanf("%d %d", &M, &K) !=2){
    if(M <= 0 || K <= 0 || M >10 || K > 10){
        printf("Invalid Input");
        return 0;
    }
    double a[10][10],col[10];
    for(int i = 0;i < M;i++){
        for(int j = 0;j < K;j++){
            scanf("%lf", &a[i][j]);
            if(a[i][j] < 0){
                printf("Invalid Input");
                return 0;
            }
        }
        col[i] = a[i][0];
    }
    
    for (int i = 0;i < M-1;i++){
        for (int j = i+1;j < M;j++){
            if (col[i] > col[j]){
                double temp = col[i];
                col[i] = col[j];
                col[j] = temp;
            }
        }
    }
    double median;
    if(M % 2 == 0)
        median =(col[M/2 - 1] + col [M/2])/2.0;
    
    else{
        median = col[M/2]; 
        printf("%.2lf",median);
    }
        return 0;
}