#include<iostream>
#include<fstream>
#include<cmath>
using namespace std;
int main()
{
freopen("heritage.in","r",stdin);
      freopen("heritage.out","w",stdout);
    int m,n,k,maxsb=-2;
    int table[258][258];
    cin>>n>>m>>k;
       for(int i=1; i<=n; i++)
           for(int j=1; j<=m; j++)
        {
            cin>>table[i][j];
            table[i][j]=table[i][j]+table[i-1][j]+table[i][j-1]-table[i-1][j-1];
        }
        for(int i=1;i<=k;i++)
        {
            if(k%i==0)
                if(n>=i && m>=k/i)
                {
                    for(int k1=i; k1<=n;k1++)
                        for(int k2=k/i;k2<=m;k2++)
                    {
                        if(table[k1][k2]-table[k1-i][k2]-table[k1][k2-k/i]+table[k1-i][k2-k/i]>maxsb)
                            maxsb=table[k1][k2]-table[k1-i][k2]-table[k1][k2-k/i]+table[k1-i][k2-k/i];
                    }
                }
        }
        if(maxsb>-1)
            cout<<maxsb<<endl;
        else
        {
            cout<<"-1\n";
        }
}