#include <iostream>
#include <cstdio>

#define f(i,beg,end) for(int i=beg; i<=end; i++)
#define inf 1000000000

using namespace std;

int n, m, k, a[30][30];

void redirect()
{
//    freopen("test.txt","r",stdin);
    freopen("minark.in","r",stdin);
    freopen("minark.out","w",stdout);
}

void init()
{
    cin >> n >> m >> k;
    
    f(i,1,n)
        f(j,1,m)
            cin >> a[i][j];
}

void solve()
{
    int ans = inf;
    
    f(r1,1,n)
        f(c1,1,m)
            f(r2,r1,n)
                f(c2,c1,m)
                {
                    int cnt = 0;
                    
                    f(i,r1,r2)
                        f(j,c1,c2)
                            cnt+=a[i][j];
                    
                    if (cnt<k) continue;
                    
                    //ans = min ( ans, (r2-r1+1)*(c2-c1+1) );
                    if (ans>(r2-r1+1)*(c2-c1+1)) ans = (r2-r1+1)*(c2-c1+1);
                }
    if (ans==inf) ans = -1;
    
    cout << ans << endl;
}

int main()
{
    redirect();
    init();
    solve();
    
    return 0;
}<!-- 0.048s -->