/*
 * main.cpp
 *
 *  Created on: Feb 17, 2013
 *      Author: krassi
 */
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
typedef unsigned uint;

const int max_n = 32;
int a[max_n][max_n], s[max_n][max_n];

int sum(int i1, int j1, int i2, int j2) {
	return s[i2][j2] + s[i1][j1] - s[i1][j2] - s[i2][j1];
}

int main(int argc, char **argv) {
	freopen("minark.in", "r", stdin);
	freopen("minark.out", "w", stdout);

	int n, m, k;
	scanf("%d%d%d", &n, &m, &k);
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < m; ++j) {
			scanf("%d", &a[i][j]);
			s[i+1][j+1] = s[i][j+1] + s[i+1][j] - s[i][j] + a[i][j];
		}
	}
	int min_s = -1;
	for (int i1 = 0; i1 < n; ++i1) {
		for (int j1 = 0; j1 < m; ++j1) {
			for (int i2 = i1; i2 <= n; ++i2) {
				for (int j2 = j1; j2 <= m; ++j2) {
					int s = sum(i1, j1, i2, j2);
					if (s >= k) {
						int area = (i2 - i1) * (j2 - j1);
						if (min_s == -1 || min_s > area) {
							min_s = area;
						}
					}
				}
			}
		}
	}
	printf("%d\n", min_s);
	return 0;
}