Untitled

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
typedef int ll;
  
set smaller_values, greater_values;
int n, k;
   
void insert_value(ll & x) {
    ll max_in_smaller_values = *smaller_values.rbegin();
      
    if(max_in_smaller_values < x) {
        greater_values.insert(x);
          
        if(greater_values.size() > k / 2) {
            ll min_in_greater = *greater_values.begin();
            smaller_values.insert(min_in_greater);
            greater_values.erase(greater_values.find(min_in_greater));
        }
    }
    else {
        smaller_values.insert(x);
          
        if(smaller_values.size() > (k + 1) / 2) {
            ll tmp_max_in_smaller = *smaller_values.rbegin();
            greater_values.insert(tmp_max_in_smaller);
            smaller_values.erase(smaller_values.find(tmp_max_in_smaller));
        }
    }
      
}
void remove_element(ll & x) {
    if(greater_values.find(x) != greater_values.end()) {
        greater_values.erase(greater_values.find(x));
    }
    else if(smaller_values.find(x) != smaller_values.end()) {
        smaller_values.erase(smaller_values.find(x));
    }
      
    if(smaller_values.empty()) {
        ll min_in_greater = *greater_values.begin();
        smaller_values.insert(min_in_greater);
        greater_values.erase(greater_values.find(min_in_greater));
    }
      
}
ll mat[888][888];
int main(){
    ios_base::sync_with_stdio(false);
//    ifstream cinx("input.txt");
    cin >> n >> k;
    ll ss = 2e9;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            cin >> mat[i][j];
            ss = min(ss, mat[i][j]);
        }
          
    }
    if(k == 1) {
        cout << ss << endl;
        return 0;
    }
    int K = k;
    k *= k;
    smaller_values.insert(mat[0][0]);
      
    for(int i = 0; i < K; i++) {
        for(int j = 0; j < K; j++) {
            if(i == 0 and j == 0) continue;
            insert_value(mat[i][j]);
        }
    }
    ll result = *smaller_values.rbegin();
    int i1 = 0, i2 = K - 1;
    int j1 = 0, j2 = K - 1;
     
    int dir = 1;
    while(i2 < n) {
        if(dir == 1) {
            result = min(result, *smaller_values.rbegin());
            
           
            if(j2 + 1 < n) {
                for(int i = i1; i <= i2; i++) {
                    remove_element(mat[i][j1]);
                }
                j1++;
                j2++;
                for(int i = i1; i <= i2; i++) {
                    insert_value(mat[i][j2]);
                }
                result = min(result, *smaller_values.rbegin());
            }
            else {
                dir = -1;
                for(int j = j1; j <= j2; j++) {
                    remove_element(mat[i1][j]);
                }

                i1++;
                i2++;
                if(i2 < n) {
                    for(int j = j1; j <= j2; j++) {
                        insert_value(mat[i2][j]);
                    }
                    result = min(result, *smaller_values.rbegin());
                }
            }
        }
        else {
            result = min(result, *smaller_values.rbegin());
             
     
            if(j1 - 1 >= 0) {
                for(int i = i1; i <= i2; i++) {
                    remove_element(mat[i][j2]);
                }
                j1--;
                j2--;
                for(int i = i1; i <= i2; i++) {
                    insert_value(mat[i][j1]);
                }
            }
            else {
                dir = 1;
                for(int j = j1; j <= j2; j++) {
                    remove_element(mat[i1][j]);
                }
                i1++;
                i2++;
                if(i2 < n) {
                    for(int j = j1; j <= j2; j++) {
                        insert_value(mat[i2][j]);
                    }
                    result = min(result, *smaller_values.rbegin());
                }
            }
        }
    }
    cout << result << endl;
     
    return 0;
}