#include<fstream.h>
int a[31][31],i,j,k,l,n,m,max,x,i1,j1;
ifstream f("teren.in");
ofstream g("teren.out");
void main(){
f>>n>>m>>k;
for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
	{f>>x;
	a[i][j]=a[i][j-1];
	if(x==1)
		a[i][j]=a[i][j-1]+1;
	a[i][j]+=a[i-1][j]-a[i-1][j-1];
	}
max=1;
for(i=1;i<n;i++)
for(j=1;j<m;j++)
	{x=a[i][j];
	i1=i;j1=j;
	while((a[i1][j]-x<=k)&&(i1<=n))
		{if((i1-i+1)*(j1-j+1)>max)
			max=(i1-i+1)*(j1-j+1);
		j1++;
		if((a[i1][j1]-x>k)||(j1>m))
			{j1=j;i1++;}
		}
	}
g<<max;
f.close();
g.close();
}