/*
ID: espr1t
TASK: 
KEYWORDS: 
CONTEST: CodeIT Round 4
*/

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <algorithm>
#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>

using namespace std;
FILE *in; FILE *out;

const int MAX = 1024;

int n, m, k;
int a[MAX][MAX];

int main(void) {
	in = stdin; out = stdout;
	in = fopen("minark.in", "rt"); out = fopen("minark.out", "wt");
	
	fscanf(in, "%d %d %d", &n, &m, &k);
	for (int i = 0; i < n; i++) {
	    for (int c = 0; c < m; c++) {
	        fscanf(in, "%d", &a[i][c]);
	    }
	}
	int ans = -1;
	for (int srow = 0; srow < n; srow++) {
	    for (int scol = 0; scol < m; scol++) {
	        for (int erow = srow; erow < n; erow++) {
	            for (int ecol = scol; ecol < m; ecol++) {
	                int sum = 0;
	                for (int row = srow; row <= erow; row++) {
	                    for (int col = scol; col <= ecol; col++) {
	                        sum += a[row][col];
	                    }
	                }
	                if (k <= sum) {
	                    if (ans == -1)
	                        ans = ((erow - srow + 1) * (ecol - scol + 1));
                        else ans = min(ans, (erow - srow + 1) * (ecol - scol + 1));
	                }
	            }
	        }
	    }
	}
	fprintf(out, "%d\n", ans);
	return 0;
}