#include<fstream.h>
ifstream f("teren.in");
ofstream g("teren.out");
int main()
{long n,m,c,a[300][2],x,i,j,k=0,nr,max=0,s,i1,i2,j1,j2;
f>>n>>m>>x;
for(i=1;i<=n;i++)
                 for(j=1;j<=m;j++)
                 {
                        f>>c;
                        if(c==1){k++;a[k][1]=i;a[k][2]=j;}
                 }
for(i1=1;i1<n;i1++)
	for(i2=i1;i2<=n;i2++)
	for(j1=1;j1<m;j1++)
        for(j2=j1;j2<=m;j2++)
        {
                nr=0;
                for(s=1;s<=k;s++)
                        if(i1<=a[s][1]&&a[s][1]<=i2&&a[s][2]<=j2&&a[s][2]>=j1)nr++;
		if(nr==x&&((i2-i1+1)*(j2-j1+1))>max)max=(i2-i1+1)*(j2-j1+1);
        }
g<<max;
f.close();
g.close();
return 0;
}