func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<long long> v;   long long a, b, f, k;   int cnt() {     int c = 0;     int n = v.size();     long long now = 0;     for (int i = 0; i < n; i++) {       if (now + b < v[i]) return -1;       while (i < n && now + b >= v[i]) i++;       i--;       c++;       now = v[i];     }     return c - 1;   }   int main() {     scanf( %I64d%I64d%I64d%I64d , &a, &b, &f, &k);     v.push_back(f);     for (long long i = 1; i < k; i++) {       if (i & 1)         v.push_back(v[i - 1] + 2 * (a - f));       else         v.push_back(v[i - 1] + 2 * f);     }     v.push_back(a * k);     printf( %d , cnt());   }   