#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <numeric>
#include <utility>

#define MAX 1024

using namespace std;

int a[MAX][MAX];
double p[MAX][MAX], e[MAX], d[MAX];

double Solve(int n, int m) {
  for (int i = 0; i < n; ++i) {
    int sum = accumulate(a[i], a[i] + m, 0);
    for (int j = 0; j < m; ++j) {
      p[i][j] = (double)a[i][j] / (double)sum;
    }
  }
  memset(e, 0, sizeof(e));
  memset(d, 0, sizeof(d));
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < m; ++j) {
      e[j] += p[i][j]; d[j] += p[i][j] * (1.0 - p[i][j]);
    }
  }
  double ret = 0;
  for (int i = 0; i < m; ++i) {
    ret += e[i] * e[i] + d[i];
  }
  return ret;
}

int main() {
  int n, m;
  while (~scanf("%d%d", &n, &m)) {
    for (int i = 0; i < n; ++i) {
      for (int j = 0; j < m; ++j) {
        scanf("%d", &a[i][j]);
      }
    }
    printf("%.2f\n", Solve(n, m));
  }
  return 0;
}