Problem p03283 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using ll = long long;
enum : int { M = (int)1e9 + 7 };
enum : ll { MLL = (ll)1e18L + 9 };
using namespace std;
#ifdef LOCAL
#include "debug_deque.hpp"
#include "rprint2.hpp"
#define vector DebugDeque
#else
#define FUNC(name)                                                             \
  template <ostream &out = cout, class... T> void name(T &&...) {}
FUNC(prints)
FUNC(printe) FUNC(printw) FUNC(printew) FUNC(printb) FUNC(printd) FUNC(printde)
    FUNC(printdu);
#endif
template <class S, class T> istream &operator>>(istream &in, pair<S, T> &p) {
  return in >> p.first >> p.second;
}
template <class T> istream &operator>>(istream &in, vector<T> &v) {
  for (auto &e : v) {
    in >> e;
  }
  return in;
}

#include <unistd.h>
struct Buffer {
  enum { chunk = 1 << 16 };
  int idx;
  char buf[chunk];
  Buffer() { init(); }
  void init() {
    idx = 0;
    read(0, buf, chunk);
  }
  void check() {
    if (idx == chunk) {
      init();
    }
  }
  int next() {
    static char notDigits[256] = {
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    };
    int ret = 0, sign = 1;
    while (check(), notDigits[(int)buf[idx]]) {
      idx++;
    }
    if (check(), buf[idx] == '-') {
      sign = -1;
      idx++;
    }
    while (check(), !notDigits[(int)buf[idx]]) {
      ret = ret * 10 + buf[idx++] - '0';
    }
    return sign * ret;
  }
};
struct FastInput {
  Buffer buf;
  template <class T> FastInput &operator>>(T &num) {
    num = buf.next();
    return *this;
  }
  void tie(int) {}
  template <class S, class T>
  friend FastInput &operator>>(FastInput &in, pair<S, T> &p) {
    return in >> p.first >> p.second;
  }
  template <class T> friend FastInput &operator>>(FastInput &in, vector<T> &v) {
    for (auto &e : v) {
      in >> e;
    }
    return in;
  }
};
FastInput fin;
#define cin fin

int accs[501][501];
int main() {
  int n, m, q;
  cin >> n >> m >> q;
  // vector<vector<int>> accs(n, vector<int>(n));
  for (int i = 0; i < m; i++) {
    int l, r;
    cin >> l >> r;
    l--;
    r--;
    accs[0][r]++;
    accs[i + 1][r]--;
    // for(int i = 0; i <= l; i++){
    //     accs[i][r]++;
    // }
  }
  for (int j = 0; j < n; j++) {
    for (int i = 1; i < n; i++) {
      accs[i][j] += accs[i - 1][j];
    }
  }
  for (int i = 0; i < n; i++) {
    for (int j = 1; j < n; j++) {
      accs[i][j] += accs[i][j - 1];
    }
  }
  for (int i = 0; i < q; i++) {
    int p, q;
    cin >> p >> q;
    p--;
    q--;
    cout << accs[p][q] << '\n';
  }
}


Fixed submission:
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using ll = long long;
enum : int { M = (int)1e9 + 7 };
enum : ll { MLL = (ll)1e18L + 9 };
using namespace std;
#ifdef LOCAL
#include "debug_deque.hpp"
#include "rprint2.hpp"
#define vector DebugDeque
#else
#define FUNC(name)                                                             \
  template <ostream &out = cout, class... T> void name(T &&...) {}
FUNC(prints)
FUNC(printe) FUNC(printw) FUNC(printew) FUNC(printb) FUNC(printd) FUNC(printde)
    FUNC(printdu);
#endif
template <class S, class T> istream &operator>>(istream &in, pair<S, T> &p) {
  return in >> p.first >> p.second;
}
template <class T> istream &operator>>(istream &in, vector<T> &v) {
  for (auto &e : v) {
    in >> e;
  }
  return in;
}

#include <unistd.h>
struct Buffer {
  enum { chunk = 1 << 16 };
  int idx;
  char buf[chunk];
  Buffer() { init(); }
  void init() {
    idx = 0;
    read(0, buf, chunk);
  }
  void check() {
    if (idx == chunk) {
      init();
    }
  }
  int next() {
    static char notDigits[256] = {
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    };
    int ret = 0, sign = 1;
    while (check(), notDigits[(int)buf[idx]]) {
      idx++;
    }
    if (check(), buf[idx] == '-') {
      sign = -1;
      idx++;
    }
    while (check(), !notDigits[(int)buf[idx]]) {
      ret = ret * 10 + buf[idx++] - '0';
    }
    return sign * ret;
  }
};
struct FastInput {
  Buffer buf;
  template <class T> FastInput &operator>>(T &num) {
    num = buf.next();
    return *this;
  }
  void tie(int) {}
  template <class S, class T>
  friend FastInput &operator>>(FastInput &in, pair<S, T> &p) {
    return in >> p.first >> p.second;
  }
  template <class T> friend FastInput &operator>>(FastInput &in, vector<T> &v) {
    for (auto &e : v) {
      in >> e;
    }
    return in;
  }
};
FastInput fin;
#define cin fin

int accs[501][501];
int main() {
  int n, m, q;
  cin >> n >> m >> q;
  // vector<vector<int>> accs(n, vector<int>(n));
  for (int i = 0; i < m; i++) {
    int l, r;
    cin >> l >> r;
    l--;
    r--;
    accs[0][r]++;
    accs[l + 1][r]--;
    // for(int i = 0; i <= l; i++){
    //     accs[i][r]++;
    // }
  }
  for (int j = 0; j < n; j++) {
    for (int i = 1; i < n; i++) {
      accs[i][j] += accs[i - 1][j];
    }
  }
  for (int i = 0; i < n; i++) {
    for (int j = 1; j < n; j++) {
      accs[i][j] += accs[i][j - 1];
    }
  }
  for (int i = 0; i < q; i++) {
    int p, q;
    cin >> p >> q;
    p--;
    q--;
    cout << accs[p][q] << '\n';
  }
}