Problem p03964 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define range(i, l, r) for (int(i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (int(i) = (r)-1; (i) >= l; (i)--)
using namespace std;
template <typename T> using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

template <typename S, typename T>
ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(";
  os << p.first << ", " << p.second;
  return os << ")";
}

template <typename T> ostream &operator<<(ostream &os, vec<T> v) {
  os << "[";
  for (int i = 0; i < v.size() - 1; i++) {
    os << v.at(i) << ", ";
  }
  return os << v.at(v.size() - 1) << "]";
}

template <typename T> ostream &operator<<(ostream &os, set<T> &s) {
  os << "{";
  if (s.begin() == s.end())
    return os << "}";
  auto it_first_item = s.begin();
  cout << *it_first_item;
  for (auto it = ++it_first_item; it != s.end(); it++) {
    cout << ", " << *it;
  }
  return cout << "}";
}

template <typename T> ostream &operator<<(ostream &os, unordered_set<T> &s) {
  os << "{";
  if (s.begin() == s.end())
    return os << "}";
  auto it_first_item = s.begin();
  cout << *it_first_item;
  for (auto it = ++it_first_item; it != s.end(); it++) {
    cout << ", " << *it;
  }
  return cout << "}";
}

template <typename K, typename V>
ostream &operator<<(ostream &os, map<K, V> m) {
  os << "{";
  if (m.begin() == m.end())
    return os << "}";
  auto it_first_item = m.begin();
  cout << it_first_item->first << ": " << it_first_item->second;
  for (auto it = ++it_first_item; it != m.end(); it++) {
    cout << ", " << it->first << ": " << it->second;
  }
  return os << "}";
}

template <typename K, typename V>
ostream &operator<<(ostream &os, unordered_map<K, V> m) {
  os << "{";
  if (m.begin() == m.end())
    return os << "}";
  auto it_first_item = m.begin();
  cout << it_first_item->first << ": " << it_first_item->second;
  for (auto it = ++it_first_item; it != m.end(); it++) {
    cout << ", " << it->first << ": " << it->second;
  }
  return os << "}";
}

lint pow(lint num, lint e, lint MOD) {
  lint res = 1;
  lint cur_num = num;
  while (e) {
    if (e & 1) {
      res *= cur_num;
      res %= MOD;
    }
    cur_num *= cur_num;
    cur_num %= MOD;
    e >>= 1;
  }
  return res;
}

int main() {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  lint N;
  cin >> N;
  vec<plint> ratio(N);
  range(i, 0, N) {
    lint T, A;
    cin >> T >> A;
    ratio.at(i) = {T, A};
  }
  lint cur_T = ratio.at(0).first, cur_A = ratio.at(0).second;
  range(i, 1, N) {
    lint T = ratio.at(i).first, A = ratio.at(i).second;
    lint m = 1;
    while (m * T < cur_T || m * A < cur_A)
      m += 1;
    cur_T = m * T, cur_A = m * A;
  }
  cout << cur_T + cur_A << "\n";
}

Fixed submission:
#include <bits/stdc++.h>
#define range(i, l, r) for (int(i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (int(i) = (r)-1; (i) >= l; (i)--)
using namespace std;
template <typename T> using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

template <typename S, typename T>
ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(";
  os << p.first << ", " << p.second;
  return os << ")";
}

template <typename T> ostream &operator<<(ostream &os, vec<T> v) {
  os << "[";
  for (int i = 0; i < v.size() - 1; i++) {
    os << v.at(i) << ", ";
  }
  return os << v.at(v.size() - 1) << "]";
}

template <typename T> ostream &operator<<(ostream &os, set<T> &s) {
  os << "{";
  if (s.begin() == s.end())
    return os << "}";
  auto it_first_item = s.begin();
  cout << *it_first_item;
  for (auto it = ++it_first_item; it != s.end(); it++) {
    cout << ", " << *it;
  }
  return cout << "}";
}

template <typename T> ostream &operator<<(ostream &os, unordered_set<T> &s) {
  os << "{";
  if (s.begin() == s.end())
    return os << "}";
  auto it_first_item = s.begin();
  cout << *it_first_item;
  for (auto it = ++it_first_item; it != s.end(); it++) {
    cout << ", " << *it;
  }
  return cout << "}";
}

template <typename K, typename V>
ostream &operator<<(ostream &os, map<K, V> m) {
  os << "{";
  if (m.begin() == m.end())
    return os << "}";
  auto it_first_item = m.begin();
  cout << it_first_item->first << ": " << it_first_item->second;
  for (auto it = ++it_first_item; it != m.end(); it++) {
    cout << ", " << it->first << ": " << it->second;
  }
  return os << "}";
}

template <typename K, typename V>
ostream &operator<<(ostream &os, unordered_map<K, V> m) {
  os << "{";
  if (m.begin() == m.end())
    return os << "}";
  auto it_first_item = m.begin();
  cout << it_first_item->first << ": " << it_first_item->second;
  for (auto it = ++it_first_item; it != m.end(); it++) {
    cout << ", " << it->first << ": " << it->second;
  }
  return os << "}";
}

lint pow(lint num, lint e, lint MOD) {
  lint res = 1;
  lint cur_num = num;
  while (e) {
    if (e & 1) {
      res *= cur_num;
      res %= MOD;
    }
    cur_num *= cur_num;
    cur_num %= MOD;
    e >>= 1;
  }
  return res;
}

int main() {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  lint N;
  cin >> N;
  vec<plint> ratio(N);
  range(i, 0, N) {
    lint T, A;
    cin >> T >> A;
    ratio.at(i) = {T, A};
  }
  lint cur_T = ratio.at(0).first, cur_A = ratio.at(0).second;
  range(i, 1, N) {
    lint T = ratio.at(i).first, A = ratio.at(i).second;
    lint m = max(cur_T / T + (cur_T % T == 0 ? 0 : 1),
                 cur_A / A + (cur_A % A == 0 ? 0 : 1));
    m = max(1LL, m);
    cur_T = m * T, cur_A = m * A;
  }
  cout << cur_T + cur_A << "\n";
}