#include<stdio.h>
#include<stdlib.h>
int compare(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 M,N;
    scanf("%d %d",&M,&N);
    if(M <= 0 || N <= 0) {
        printf("Invalid input");
        return 0;
    }
   float arr[M][N];
   int valid = 0;
   for(int i = 0; i < M ; i++) {
       for(int j = 0; j < N; j++ );
    scanf("%f",&arr[i][j]);
    if(arr[i][j] < 0)
    invalid = 1;
   }
}
if(invalid) {
    printf("Invalid input");
    return 0;
}
float firstcol[M];
for(int i = 0; i < M; i++)
firstcol[i] = arr[i][0];
qsort(firstcol, M , sizeof(float), compare);
int total = M * N;
float median;
if( M % 2 == 0)
median = (firstcol[m/2 - 1] + firstcol[M/2]) / 2.0;
else
median = firstcol[M/2];
printf("%.2f",median);
return 0;
}