#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define f first
#define s second
#ifdef BALBIT
#define bug(...) cerr<<"#"<<__LINE__<<": "<<#__VA_ARGS__<<": ", _do(__VA_ARGS__)
template<typename T> void _do(T && x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T && x, S && ...y){cerr<<x<<", "; _do(y...);}
#define IOS()
#else
#define IOS() ios::sync_with_stdio(0), cin.tie(0)
#define endl '\n'
#define bug(...)
#endif
#define REP(i,n) for (int i = 0; i<n; ++i)
#define REP1(i,n) for (int i = 1; i<=n; ++i)
const int maxn = 2505;
bool b[maxn][maxn];
signed main(){
IOS();
bug(1,2);
int n,m; cin>>n>>m;
REP1(i,n) REP1(j,m) {
char c; cin>>c; b[i][j] = c=='1';
}
int H = 10000000, W = 10000000;
REP1(i,n) REP1(j,m) {
if (b[i][j] && !b[i][j-1]) {
int k = 0;
for (int J = j; b[i][J]; ++J, ++k);
W = min(W, k);
}
if (b[i][j] && !b[i-1][j]) {
int k = 0;
for (int I = i; b[I][j]; ++I, ++k);
H = min(H, k);
}
}
bug(H,W);
if (H == 10000000) assert(0);
cout<<H*(ll)W<<endl;
}
