#include<stdio.h>
#include<stdlib.h>
#define TRUE 1
#define FALSE 0

#define CONNECTED 1
#define NOT_CONNECTED 0
#define VISITED 1
#define NOT_VISITED 0
#define MAX 10000
#define UNASSIGNED -1

int compare(const void* a, const void* b)
{
	return 0;
}
int main(void)
{
	int i,j,k,l;
	int p,d,m,s;
	scanf("%d %d %d %d",&p,&d,&m,&s);
	int count;
	count=0;
	while(s>=p)
	{
		s=s-p;
		count++;
		p=p-d;
		if(p<m)
			p=m;
	}
	printf("%d\n",count);
	return 0;
}