Language: C++

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstring>
#include <deque>
#include <forward_list>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
typedef long long ll;
typedef pair<int, int> P;
typedef bitset<16> BS;

const ll MOD = 1E+09 + 7;
const ll INF = 1E18;
const int MAX_N = 1E+05;
const int MAX_K = 1000;

ll N, K;

ll sum[4 * MAX_K + 1][4 * MAX_K + 1];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> N >> K;

    for (int i = 1; i <= N; i++) {
        ll x, y;
        char c;
        cin >> x >> y >> c;
        if (c == 'W') {
            mod[x % (2 * K) + 1][(y + K) % (2 * K) + 1]++;
        } else {
            mod[x % (2 * K) + 1][y % (2 * K) + 1]++;
        }
    }

    for (int i = 0; i < 4 * K; i++) {
        for (int j = 0; j < 4 * K; j++) {
            mod[i + 1][j + 1] = mod[i % (2 * K) + 1][j % (2 * K) + 1];
        }
    }

    for (int i = 1; i <= 4 * K; i++) {
        for (int j = 1; j <= 4 * K; j++) {
            mod[i][j] += mod[i - 1][j] + mod[i][j - 1] - mod[i - 1][j - 1];
        }
    }

    ll ans = 0;
    for (int i = 1; i <= 2 * K; i++) {
        for (int j = 1; j <= 2 * K; j++) {
            ll res = 0;
            res += mod[i + 2 * K - 1][j + 2 * K - 1] - mod[i + K - 1][j + 2 * K - 1] - mod[i + 2 * K - 1][j + K - 1] + mod[i + K - 1][j + K - 1];
            res += mod[i + K - 1][j + K - 1] - mod[i + K - 1][j - 1] - mod[i - 1][j + K - 1] + mod[i - 1][j - 1];
            ans = max(res, ans);
        }
    }

    /*
    for (int i = 1; i <= 2 * K; i++) {
        for (int j = 1; j <= 2 * K; j++) {
            cout << "i = " << i << ", j = " << j << ", sum = " << sum[i][j] << "\n";
        }
    }
    */

    cout << ans << "\n";

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:50:13: error: 'mod' was not declared in this scope; did you mean 'modf'?
   50 |             mod[x % (2 * K) + 1][(y + K) % (2 * K) + 1]++;
      |             ^~~
      |             modf
a.cc:52:13: error: 'mod' was not declared in this scope; did you mean 'modf'?
   52 |             mod[x % (2 * K) + 1][y % (2 * K) + 1]++;
      |             ^~~
      |             modf
a.cc:58:13: error: 'mod' was not declared in this scope; did you mean 'modf'?
   58 |             mod[i + 1][j + 1] = mod[i % (2 * K) + 1][j % (2 * K) + 1];
      |             ^~~
      |             modf
a.cc:64:13: error: 'mod' was not declared in this scope; did you mean 'modf'?
   64 |             mod[i][j] += mod[i - 1][j] + mod[i][j - 1] - mod[i - 1][j - 1];
      |             ^~~
      |             modf
a.cc:72:20: error: 'mod' was not declared in this scope; did you mean 'modf'?
   72 |             res += mod[i + 2 * K - 1][j + 2 * K - 1] - mod[i + K - 1][j + 2 * K - 1] - mod[i + 2 * K - 1][j + K - 1] + mod[i + K - 1][j + K - 1];
      |                    ^~~
      |                    modf