#include<bits/stdc++.h>
using namespace std;
int n,m,ans=0,k;
int a[105][105];
bool book(int i,int j,int x,int y){
	int bak=0;
	for (int k=i;k<=x;k++){
		for (int l=j;l<=y;l++){
			if (a[k][l]) bak++;
		}
	}
	return bak==k;
}
int main(){
    cin>>n>>m>>k;
    for (int i=1;i<=n;i++){
    	for (int j=1;j<=m;j++){
    		char x;
    		cin>>x;
    		a[i][j]=x-'0';
		}
	}
	for (int i=1;i<=n;i++){
		for (int j=1;j<=m;j++){
			for (int x=i;x<=n;x++){
				for (int y=j;y<=m;y++){
					if (x==i&&y==j) continue;
					if (book(i,j,x,y)) ans=max(ans,(x-i+1)*(y-j+1));
				}
			}
		}
	} 
	cout<<ans;
	return 0;
}