#include <stdio.h>
#include <stdlib.h>

int N, M, K;
int A[20][20];

int main() {

    FILE *fin = fopen("minark.in", "r");
    FILE *fout = fopen("minark.out", "w");
    int x1, y1, x2, y2, i, j, l, s, minl = -1;

    fscanf(fin, "%d %d %d", &N, &M, &K);

    for (i = 0; i < N; i++)
        for (j = 0; j < M; j++)
            fscanf(fin, "%d", &A[i][j]);

    for (x1 = 0; x1 < N; x1++)
        for (y1 = 0; y1 < M; y1++)
            for (x2 = x1; x2 < N; x2++)
                for (y2 = y1; y2 < M; y2++) {

                    s = 0;
                    l = (x2-x1+1)*(y2-y1+1);

                    for (i = x1; i <= x2; i++)
                        for (j = y1; j <= y2; j++)
                            s += A[i][j];

                    //printf("[%d][%d]-[%d][%d] = %d\n", x1, y1, x2, y2, s);

                    if (s >= K && (l < minl || minl == -1))
                    {
                        minl = l;
                    }
                }

    fprintf(fout, "%d", minl);

    return 0;
}<!-- 0.0401s -->