#define _CRT_SECURE_NO_DEPRECATE
#include <iostream> 
#include <string>
#include <vector>
#include <sstream>
#include <queue>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <math.h>
#include <stack>
#include <deque>
#include <numeric>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <bitset>
#define mpair make_pair
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
typedef long double ld;
const ld epsylon = 1e-9;
int main()
{
  freopen("minark.in","r",stdin);
  freopen("minark.out", "w", stdout);

  int n,m, K;
  cin >> n >> m  >> K;
  vector<vector<int> > a(n+1, vector<int>(m+1, 0));

  for (int i=0;i<n;++i) {
    for (int j=0;j<m;++j){
      cin >> a[i+1][j+1];
    }
  }
  
  for (int i=1;i<=n;++i){
    for (int j=1; j <= m;++j){
      a[i][j] = a[i][j] + a[i-1][j] + a[i][j-1] - a[i-1][j-1];
    }
  }

  int best = -1;
  for (int i=0;i<n;++i){
    for (int j=0;j<m;++j) {
      for (int k=i;k<n;++k){
        for(int l=j;l<m;++l){
          int  val = a[k+1][l+1] - a[i][l+1] - a[k+1][j] + a[i][j];
          if (val >= K) {
            int area = (k-i+1)*(l-j+1);

            if (best == -1 || area < best) {
              best = area;
            }
          }
        }
      }
    }
  }

  cout << best << endl;
  return 0;
}
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