#include <iostream>

long int numGames(int p, int d, int m, int s) {
  long int count = 0;
  while(s - p >= 0) {
    s -= p;
    if(p - d > m) {
      p -= d;
    } else {
      p = m;
    }


    count++;
  }

  return count;
}

int main() {
  int m, p, d, s;
  std::cin >> p >> d >> m >> s;
  std::cout << numGames(p, d, m, s) << std::endl;
}