func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<long long> v;   int main() {     long long a, b, f, k;     cin >> a >> b >> f >> k;     if (b / a >= k) {       cout << 0 << endl;       return 0;     }     v.push_back(f);     for (long long i = 2;; i += 2) {       long long r1 = i * a - f;       long long r2 = i * a + f;       if (r1 > k * a) break;       if (r1 <= k * a) v.push_back(r1);       if (r2 <= k * a) v.push_back(r2);     }     v.push_back(k * a);     if (b < f) {       cout << -1;       return 0;     }     long long last = 0;     long long has = b;     int sum = 0;     for (int i = 0; i < v.size(); i++) {       long long dis = v[i] - last;       if (dis > has) {         has = b;         sum++;       }       if (has < dis) {         cout << -1 << endl;         return 0;       }       has -= dis;       last = v[i];     }     cout << sum << endl;     return 0;   }   