#include <bits/stdc++.h>
using namespace std;
long long fpm(long long b, long long e, long long m) {
  long long t = 1;
  for (; e; e >>= 1, b = b * b % m) e & 1 ? t = t * b % m : 0;
  return t;
}
template <class T>
inline bool chkmin(T &a, T b) {
  return a > b ? a = b, true : false;
}
template <class T>
inline bool chkmax(T &a, T b) {
  return a < b ? a = b, true : false;
}
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <class edge>
struct Graph {
  vector<vector<edge> > adj;
  Graph(int n) {
    adj.clear();
    adj.resize(n + 5);
  }
  Graph() { adj.clear(); }
  void resize(int n) { adj.resize(n + 5); }
  void add(int s, edge e) { adj[s].push_back(e); }
  void del(int s, edge e) { adj[s].erase(find(iter(adj[s]), e)); }
  int deg(int v) { return adj[v].size(); }
  vector<edge> &operator[](int t) { return adj[t]; }
};
const int maxn = 3300, maxm = 330;
double P[maxn][maxm], key[maxn], f[maxn][maxn], g[maxn];
int main() {
  ios_base::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; ++i)
    for (int j = 1, t; j <= m; ++j) cin >> t, P[i][j] = t / 1000.0;
  for (int i = 1; i <= m; ++i) {
    for (int j = 0; j <= n; ++j) f[i][j] = j ? f[i][j - 1] * (1 - P[j][i]) : 1;
    key[i] = f[i][n];
  }
  double ans = 0;
  for (int i = 1; i <= n; ++i) {
    int x = min_element(key + 1, key + m + 1) - key;
    for (int j = 1; j <= n; ++j)
      g[j] = g[j - 1] * (1 - P[j][x]) + f[x][j - 1] * P[j][x];
    memcpy(f[x], g, sizeof(g));
    ans += 1 - key[x];
    key[x] += f[x][n];
  }
  cout << setprecision(20) << ans << endl;
  return 0;
}
