#include<iostream>
#include<fstream>
#include<vector>
#include<climits>

using namespace std;

long long n,m,k;
bool a[260][260];

long long dp[260][260];

long long dividers_size;
vector <long long> dividers;

void start_full()
{
    for(long long j = 0;j<m;j++)
        dp[0][j] = a[0][j];

}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    ifstream  input("heritage.in");
    ofstream  output("heritage.out");

    long long max_sum = 0;
    long long current_sum = 0;

    input >> n >> m >> k;
    for(long long i = 0;i<n;i++)
        for(long long j = 0;j<m;j++)
            input >> a[i][j];

    for(long long i = 1;i<=k/2;i++)
        if(k%i==0 && i<=n && k/i<=m) dividers.push_back(i);

    start_full();
    dividers_size = dividers.size();
    for(long long j = 0;j<m;j++)
        for(long long i = 1;i<n;i++)
            dp[i][j] = dp[i-1][j] + a[i][j];

    for(long long d = 0;d<dividers_size;d++)
    {
        //dividers[d] -> i
        //k/dividers[d] -> j

        for(long long i = dividers[d]-1;i<n;i++)
        {
            current_sum = 0;
            for(long long j = 0;j<m-(k/dividers[d]-1);j++)
            {
                current_sum = 0;
                for(long long x = 0;x<k/dividers[d];x++)
                    if(i==dividers[d]-1) current_sum = current_sum + dp[i][j+x];
                    else  current_sum = current_sum + (dp[i][j+x] - dp[i-dividers[d]][j+x]);

                if(current_sum>max_sum) max_sum = current_sum;

            }


        }
    }

    if(max_sum==0) output << "-1" << endl;
    else output << max_sum << endl;
}


/*
long long min_deep = long long_MAX;
long long current_deep = 0;

long long max = 0;

    for(long long i = 0;i<n;i++)
    {
        for(long long j = 0;j<m;j++)
        {

            min_deep =  long long_MAX;;
            for(long long y = j;y<m;y++)
            {
                current_deep = 0;
                if(min_deep==long long_MAX)
                {
                    for(long long x = i;x<n;x++)
                        if(a[x][y]==true) current_deep++;
                            else break;

                        min_deep = current_deep;
                    }
                    else
                    {
                        for(long long x = i;x<i+min_deep;x++)
                            if(a[x][y]==true) current_deep++;
                            else break;

                        if(min_deep>current_deep) min_deep = current_deep;
                    }

                    if(min_deep*(y-j+1)==k)
                }
            }

        }
    }
    */