#include <bits/stdc++.h>
using namespace std;
int qzh[105][105];
int main(){
    ios::sync_with_stdio(false);
    int n,m,k,ans=INT_MAX;
    cin>>n>>m>>k;
    for(int i=1;i<=n;i++){
        string x;
        cin>>x;
        for(int j=1;j<=m;j++){
            qzh[i][j]=qzh[i-1][j]+qzh[i][j-1]-qzh[i-1][j-1]+x[j-1]-'0';
        }
    }
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            for(int ii=i;i<=n;i++)
                for(int jj=j;jj<=m;jj++){
                    int temp=qzh[ii][jj]-qzh[ii][j-1]-qzh[i-1][jj]+qzh[i-1][j-1];
                    if(temp>=k)ans=min(ans,(ii-i+1)*(jj-j+1));
                }
    if(ans=0x3f3f3f3f)cout<<0;
    else cout<<ans;
    return 0;
}