#include <bits/stdc++.h>   using namespace std;   const int mod = 1e9 + 7;   const double EPS = 1e-9;   const int INF = 1 << 29;   int const NN = 5e3 + 3;   int const MX = 1e9 + 9;   int a[505][505];   int mx[505][505];   int main() {     int n, m, K, q;     cin >> n >> m >> K >> q;     for (int i = 1; i <= n; ++i) {       for (int j = 1; j <= m; ++j) a[i][j] = MX;     }     while (q--) {       int x, y, t;       cin >> x >> y >> t;       a[x][y] = t;     }     int ans = MX;     for (int i = 1; i <= n; ++i) {       for (int j = 1; j <= m; ++j) {         mx[i][j] = a[i][j];         for (int k = 2; i + k - 1 <= n && k <= K; ++k) {           mx[i][j] = max(mx[i][j], a[i + k - 1][j]);         }       }     }     for (int i = 1; i + K - 1 <= n; ++i) {       for (int j = 1; j + K - 1 <= m; ++j) {         int mxx = -1;         for (int jj = j; jj <= j + K - 1; ++jj) {           mxx = max(mxx, mx[i][jj]);         }         ans = min(ans, mxx);       }     }     if (ans < MX) {       printf( %d , ans);       ;       putchar(  n );     } else       puts( -1 );     return 0;   }   