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

void score_average(int M, int N, float (*score)[N])
{
    int i, j;
    float sum = 0.0, ave;
    for(i = 0; i < M; i++)
    {
        for(j = 0; j < N; j++)
        {
            sum = sum + score[i][j];
        }
    }
    ave = sum / (M * N);
    printf("%.1f\n", ave);
}

int main()
{
    int M, N;
    scanf("%d", &M);
    scanf("%d", &N);
    float score[M][N];
    int i, j;
    for(i = 0; i < M; i++)
    {
        for(j = 0; j < N; j++)
        {
            scanf("%f", &score[i][j]);
        }
    }
    score_average(M, N, score);
    return 0;
}