#include<stdio.h>
#include<string.h>
#include<algorithm>

using namespace std;

int main()
{
	int p,d,m,s,flag=1,cnt;
	
	scanf("%d %d %d %d",&p,&d,&m,&s);
	int kurang = p;
	cnt=0;
	while(flag==1)
	{
		if(kurang<=m)
		{
			kurang = m;
		}
		if(s<kurang)
		{
			break;
		}
		s -= kurang;
		kurang -= d;
		cnt++;
	}
	printf("%d\n",cnt);
}