#include <stdio.h>
#include <string.h>
#include <string>
#include <vector>
#include <sstream>
#include <algorithm>
#include <iostream>
#include <cmath>
#include <map>
using namespace std;

#define FOR(i,n) for (int i = 0; i < n; i++)
#define abs(x) ((x)<0?(-(x)):(x))
#define REP(i,v) for (unsigned i = 0; i < v.size(); i++)
#define RL(i,v) for (unsigned i = 0; i < v.length(); i++)
typedef long long ll;

int m[30][30];

int main(void)
{
#ifdef __LOCAL__
	freopen("problem1.in", "r", stdin);
#else
	freopen("minark.in", "r", stdin);
 	freopen("minark.out", "w", stdout);
#endif
    int N,M,K;
    cin>>N>>M>>K;
    FOR(i,N)FOR(j,M)cin>>m[i][j];
    //cout<<N<<M<<K<<endl;

    bool found = false;
    int result = 0;

    FOR(i,N)FOR(j,M) {
        for(int ii=i;ii<N;ii++)
            for(int jj=j;jj<M;jj++) {
                int sum = 0;
                bool aFound = false;
                for(int k=i;k<=ii;k++)
                    for(int l=j;l<=jj;l++) {
                        sum+=m[k][l];
                    }
                int area = (ii-i+1)*(jj-j+1);
                if(sum>=K && (!found || area < result)) {
                    //cout<<i<<" "<<j<<" "<<ii<<" "<<jj<<" "<<sum<<endl;
                    result = area;
                    found = true;
                }
            }
    }

    if(found)cout<<result<<endl;
    else cout<<(-1)<<endl;
    return 0;
}
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