#include <iostream>

using namespace std;

int main(){
	int m,s,d,p;
	cin >>p >>d >>m >>s;
	int count=0, curr = 0,spent=0;
	if(s > p){
		count ++;
		spent = p;
	}
	else{
		cout <<"0"<<endl;
		return 0;
	}
	curr = p;
	while(s > 0){
		curr = max(m,curr-d);
		if(spent + curr <= s){
			count++;
			spent+= curr;
		}
		else
			break;
	}
	cout <<count<<endl;
	return 0;
}