#include<iostream>
#include<fstream>
#include<cstdio>
#include<algorithm>
using namespace std;
long long n,m,k,min1,a,dp[21][21];
int main()
{
	freopen("minark.in","r",stdin);
	freopen("minark.out","w",stdout);
	scanf("%lld%lld%lld",&n,&m,&k);
	min1=2000000001;
	for(int i=1; i<=n; i++)
    {
        for(int j=1; j<=m; j++)
        {
            scanf("%lld",&a);
            dp[i][j]=dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1]+a;
        }
    }
    for(int i=1; i<=n; i++)
    {
        for(int j=1; j<=m; j++)
        {
            for(int l=i; l<=n; l++)
            {
                for(int p=j; p<=m; p++)
                {
                    long long t=dp[l][p]-dp[i-1][p]-dp[l][j-1]+dp[i-1][j-1];
                    if(t>=k) min1=min(min1,(long long)(l-i+1)*(p-j+1));
                }
            }
        }
    }
    if(min1==2000000001) printf("-1\n");
    else printf("%lld\n",min1);
	return 0;
}