Problem p03505 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RANGE(i, a, b) for (int i = (a); i < (b); ++i)
#define RREP(i, n) for (int i = (n)-1; i >= 0; --i)

#define endl '\n'
#define pb push_back
#define eb emplace_back
#define pque priority_queue
#define umap unordered_map
#define BIG 2000000000
#define VERYBIG 1000000000000000ll
#define PI 3.141592653589793238
#define dcout cout << fixed << setprecision(20)

const long long dx[] = {1, 0, -1, 0, 1, 1, -1, -1},
                dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
const long long MOD = 1e9 + 7;

// typedef long long ll;
#define int long long
#define double long double

template <typename T> inline T GCD(T a, T b) {
  T c;
  while (b != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
template <typename T> inline T LCM(T a, T b) {
  T c = GCD(a, b);
  a /= c;
  return a * b;
}
template <typename T> inline T nCr(T a, T b) {
  T i, r = 1;
  for (i = 1; i <= b; i++) {
    r *= (a + 1 - i);
    r /= i;
  }
  return r;
}
template <typename T> inline T nHr(T a, T b) { return nCr(a + b - 1, b); }

typedef pair<int, int> INTP;
typedef vector<int> INTV;
struct edge2 {
  int to, cost;
};
struct edge3 {
  int from, to, cost;
};

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int K, A, B;
  cin >> K >> A >> B;
  if (A - B <= 0 and A < K)
    cout << -1 << endl;
  else {
    int plus = A - B;
    int ans = 1;
    K -= A;
    ans += (K + plus - 1) / plus * 2;
    cout << ans << endl;
  }
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RANGE(i, a, b) for (int i = (a); i < (b); ++i)
#define RREP(i, n) for (int i = (n)-1; i >= 0; --i)

#define endl '\n'
#define pb push_back
#define eb emplace_back
#define pque priority_queue
#define umap unordered_map
#define BIG 2000000000
#define VERYBIG 1000000000000000ll
#define PI 3.141592653589793238
#define dcout cout << fixed << setprecision(20)

const long long dx[] = {1, 0, -1, 0, 1, 1, -1, -1},
                dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
const long long MOD = 1e9 + 7;

// typedef long long ll;
#define int long long
#define double long double

template <typename T> inline T GCD(T a, T b) {
  T c;
  while (b != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
template <typename T> inline T LCM(T a, T b) {
  T c = GCD(a, b);
  a /= c;
  return a * b;
}
template <typename T> inline T nCr(T a, T b) {
  T i, r = 1;
  for (i = 1; i <= b; i++) {
    r *= (a + 1 - i);
    r /= i;
  }
  return r;
}
template <typename T> inline T nHr(T a, T b) { return nCr(a + b - 1, b); }

typedef pair<int, int> INTP;
typedef vector<int> INTV;
struct edge2 {
  int to, cost;
};
struct edge3 {
  int from, to, cost;
};

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int K, A, B;
  cin >> K >> A >> B;
  if (A - B <= 0 and A < K)
    cout << -1 << endl;
  else if (A - B <= 0 and A >= K)
    cout << 1 << endl;
  else {
    int plus = A - B;
    int ans = 1;
    K -= A;
    ans += (K + plus - 1) / plus * 2;
    cout << ans << endl;
  }
}