bk.cpp

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
template<class T> using uset = unordered_set<T>;
template<class T, class U> using umap = unordered_map<T, U>;
template<class T> using mset = multiset<T>;
template<class T, class U> using mmap = multimap<T, U>;
template<class T> using umset = unordered_multiset<T>;
template<class T, class U> using ummap = unordered_multimap<T, U>;

#define REP(i, n, m) for(ll i=n; i<(ll)m; ++i)
#define IREP(i, n, m) for(ll i=n-1; i>=m; --i)
#define rep(i, n) REP(i, 0, n)
#define irep(i, n) IREP(i, n, 0)
#define all(v) v.begin(), v.end()
#define vprint(v) for(auto e:v){cout<<e<<" ";};cout<<endl;
#define vvprint(vv) for(auto v:vv){vprint(v)};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(20);

    ll H, W;
    cin >> H >> W;
    vvll P(H, vll(W, 0));
    rep(i, H) rep(j, W) cin >> P[i][j];

    ll ans = 0;

    REP(i, 1, 1<<H){
        vll rows;
        rep(j, H){
            if((i>>j)&1) rows.push_back(j);
        }
        vll count(H*W+1, 0);
        rep(j, W){
            bool ok = true;
            ll n = P[rows[0]][j];
            REP(k, 1, rows.size()){
                if(P[rows[k]][j]!=n){
                    ok = false;
                    break;
                }
            }
            if(ok) ++count[n];
        }
        ll mcol = 0;
        rep(j, H*W+1) mcol = max(mcol, count[j]);
        ans = max(ans, mcol*((ll)rows.size()));
    }
    cout << ans << endl;
}