UVa 10074

#include <bits/stdc++.h>
///for ordered set///
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>

using namespace std;
///For ordered set///
// using namespace __gnu_pbds;
///For ordered set///
// typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;

///Compiler Optimizer///
// #pragma GCC optimize("Ofast,no-stack-protector")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #pragma GCC optimize("unroll-loops")

///define///
#define ll          long long int
#define all(v)      v.begin(),v.end()
#define rall(v)     v.rbegin(),v.rend()
#define unq(s)      sort(all(s)),(s).erase(unique(all(s)),s.end())
#define pb          push_back
#define pob         pop_back
#define MP          make_pair
#define ff          first
#define ss          second
#define Log(b,x)    (log(x)/log(b))
#define clr(a,x)    memset(a,x,sizeof(a))
#define vout(v,sz)  for(int w=0;w<sz;w++){if(w) spc; cout<<v[w];}
///IO///
#define sc          scanf
#define pf          printf
#define cspf(i)     pf("Case #%d: ", i)
#define spc         pf(" ")
#define line        pf("\n")
#define sc1(x)      sc("%d", &x)
#define sc2(x,y)    sc("%d %d", &x, &y)
#define scl1(x)     sc("%lld", &x)
#define pf1(x)      pf("%d",x)
#define pfl1(x)     pf("%lld",x)
#define fastIO      ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr)
///constants///
#define MOD         (int)(998244353)
#define MaxN        100000
#define inf         0x3f3f3f3f
#define PI          acos(-1.0)  // 3.1415926535897932
#define eps         1e-6

#ifdef ERFANUL007
    #define debug(...) __f(#__VA_ARGS__, __VA_ARGS__)
    template < typename Arg1 >
    void __f(const char* name, Arg1&& arg1){
        cout << name << " = " << arg1 << std::endl;
    }
    template < typename Arg1, typename... Args>
    void __f(const char* names, Arg1&& arg1, Args&&... args){
        const char* comma = strchr(names, ',');
        cout.write(names, comma - names) << " = " << arg1 <<" | ";
        __f(comma+1, args...);
    }
#else
    #define debug(...)
#endif

template <class T> inline T bigMod(T p,T e,T M){T ret=1; for(;e>0;e>>=1){ if(e&1) ret=(ret*p)%M; p=(p*p)%M;} return (T)ret;}
template <class T> inline T modInverse(T a,T M){return bigMod(a,M-2,M);}
template <class T> inline T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);}
template <class T> inline T lcm(T a,T b) {a=abs(a);b=abs(b); return (a/gcd(a,b))*b;}

int dx[] = { 1,-1, 0, 0};                //graph moves
int dy[] = { 0, 0, 1,-1};               //graph moves


int main()
{
    #ifdef ERFANUL007
        clock_t tStart = clock();
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif

    int n, m;

    while(~sc2(n, m) && n && m){
        int grid[n+1][m+1], sum[n+1][m+1];
        for(int i=0; i<=n; i++) sum[i][0] = 0;
        for(int j=0; j<=m; j++) sum[0][j] = 0;
        for(int i=1; i<=n; i++){
            for(int j=1; j<=m; j++){
                sc1(grid[i][j]);
                sum[i][j] = sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1] + grid[i][j];
            }
        }
        int ans = 0;
        for(int i=1; i<=n; i++){
            for(int j=1; j<=m; j++){
                for(int k=i; k<=n; k++){
                    for(int l=j; l<=m; l++){
                        int val = sum[k][l] - sum[k][j-1] - sum[i-1][l] + sum[i-1][j-1];
                        if(val == 0){
                            ans = max(ans, (k-i+1)*(l-j+1));
                            // debug(i, j, k, l, ans);
                        }
                    }
                }
            }
        }
        printf("%d\n", ans);
    }


    #ifdef ERFANUL007
        fprintf(stderr, "\n>> Runtime: %.10fs\n", (double) (clock() - tStart) / CLOCKS_PER_SEC);
    #endif

    return 0;
}