#include<stdio.h>
#include<stdlib.h>
int main(){
    int M,N;
        scanf("%d %d",&M,&N);
        if(M<=0 || N<=0){
            printf("Invalid input");
            return 0;
        }
        
        
        float prices[10][10];
        float fristCol[10];
        
        for(int i=0;i<M;i++){
            for(int j=0;j<N;j++){
                scanf("%f", &prices[i][j]);
                if(prices[i][j]<0){
                    printf("Invalid input");
                    return 0;
                }
            }
            firstCol[i] = prices[i][0];
        }
        for(int i=0;i<M-1;i++){
            for(int j=i=1;j<M;j++){
                if(firstCol[i]> firstCol[j]){
                    float temp = firstCol[i];
                    firstCol[i] = firstCol[j];
                    firstCol[j] = temp;
                }
            }
        }
    }
    float median;
    if (M % 2 == 1){
        median = firstCol[M / 2];
        }else{
            median = (firstCol[M / 2 - 1] + firstCol[m / 2])/2.0;
        }
         
         printf("%.2f", median);
         return 0;
}