Problem p02941 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
// #include <boost/multiprecision/cpp_int.hpp>
#pragma GCC optimize("O3")
#define REP(i, n) for (int i = 0; i < n; i++)
#define REPP(i, n) for (int i = 1; i <= n; i++)
#define ALL(obj) (obj).begin(), (obj).end()
#define EPS (1e-9)
#define INF (1e17)
#define PI (acos(-1))
// const double PI = acos(-1);
// const double EPS = 1e-15;
// long long INF=(long long)1E17;
#define i_7 (long long)(1e9 + 7)
// #define i_7 998'244'353
long mod(long a) {
  long long c = a % i_7;
  if (c >= 0)
    return c;
  return c + i_7;
}
long long po(long a, long b) {
  if (b == 0) {
    return 1;
  }

  long long z = po(a, b / 2);
  z = mod(z * z);
  if (b % 2 != 0) {
    z = mod(a * z);
  }
  return z;
}
using namespace std;
// using namespace boost::multiprecision;

bool prime_(int n) {
  if (n == 1) {
    return false;
  } else if (n == 2) {
    return true;
  } else {
    for (int i = 2; i <= sqrt(n); i++) {
      if (n % i == 0) {
        return false;
      }
    }
    return true;
  }
}

long long gcd_(long long a, long long b) {
  if (a < b) {
    swap(a, b);
  }
  if (a % b == 0) {
    return b;
  } else {
    return gcd_(b, a % b);
  }
}

long long lcm_(long long x, long long y) { return (x / gcd_(x, y)) * y; }

int main() {

  int n;
  cin >> n;
  int a[n], b[n];
  REP(i, n) { cin >> a[i]; }
  REP(i, n) { cin >> b[i]; }
  priority_queue<pair<int, int>> q;
  REP(i, n) { q.push(make_pair(b[i], i)); }
  long long ans = 0;
  while (!q.empty()) {
    int val = q.top().first;
    int i = q.top().second;
    q.pop();
    if (val == a[i]) {
      continue;
    }
    if (val < a[i]) {
      cout << -1 << endl;
      return 0;
    }
    int l = i - 1, r = i + 1;
    if (l < 0) {
      l = n - 1;
    }
    if (r >= n) {
      r = 0;
    }
    long long cnt;
    cnt = (b[i] - a[i]) / (b[l] + b[r]);
    ans += cnt;
    b[i] -= cnt * (b[l] + b[r]);
    q.push(make_pair(b[i], i));
  }
  cout << ans << endl;
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
// #include <boost/multiprecision/cpp_int.hpp>
#pragma GCC optimize("O3")
#define REP(i, n) for (int i = 0; i < n; i++)
#define REPP(i, n) for (int i = 1; i <= n; i++)
#define ALL(obj) (obj).begin(), (obj).end()
#define EPS (1e-9)
#define INF (1e17)
#define PI (acos(-1))
// const double PI = acos(-1);
// const double EPS = 1e-15;
// long long INF=(long long)1E17;
#define i_7 (long long)(1e9 + 7)
// #define i_7 998'244'353
long mod(long a) {
  long long c = a % i_7;
  if (c >= 0)
    return c;
  return c + i_7;
}
long long po(long a, long b) {
  if (b == 0) {
    return 1;
  }

  long long z = po(a, b / 2);
  z = mod(z * z);
  if (b % 2 != 0) {
    z = mod(a * z);
  }
  return z;
}
using namespace std;
// using namespace boost::multiprecision;

bool prime_(int n) {
  if (n == 1) {
    return false;
  } else if (n == 2) {
    return true;
  } else {
    for (int i = 2; i <= sqrt(n); i++) {
      if (n % i == 0) {
        return false;
      }
    }
    return true;
  }
}

long long gcd_(long long a, long long b) {
  if (a < b) {
    swap(a, b);
  }
  if (a % b == 0) {
    return b;
  } else {
    return gcd_(b, a % b);
  }
}

long long lcm_(long long x, long long y) { return (x / gcd_(x, y)) * y; }

int main() {

  int n;
  cin >> n;
  int a[n], b[n];
  REP(i, n) { cin >> a[i]; }
  REP(i, n) { cin >> b[i]; }
  priority_queue<pair<int, int>> q;
  REP(i, n) { q.push(make_pair(b[i], i)); }
  long long ans = 0;
  while (!q.empty()) {
    int val = q.top().first;
    int i = q.top().second;
    q.pop();
    if (val == a[i]) {
      continue;
    }
    if (val < a[i]) {
      cout << -1 << endl;
      return 0;
    }
    int l = i - 1, r = i + 1;
    if (l < 0) {
      l = n - 1;
    }
    if (r >= n) {
      r = 0;
    }
    long long cnt;
    cnt = (b[i] - a[i]) / (b[l] + b[r]);
    if (cnt == 0) {
      cout << -1 << endl;
      return 0;
    }
    ans += cnt;
    b[i] -= cnt * (b[l] + b[r]);
    q.push(make_pair(b[i], i));
  }
  cout << ans << endl;
  return 0;
}