

import java.util.Scanner;

public class Solution {

	final int obs =1;
	public int Isearch(int p,int a,int b,int t,String photo,int total)
	{
		int photos=0;
		if(photo.charAt(0)=='w')
			total+=b;
		total+=obs;
		if(total<=t)
			photos++;
		total+=a;
		if(total>=t)
			return photos;
		else
		{
			int m=1;
			return Isearchright(p,a,b,t,photo,m,total)>=Isearchleft(p,a,b,t,photo,total)?photos+Isearchright(p,a,b,t,photo,m,total):photos+Isearchleft(p,a,b,t,photo,total);
		}
	}
	public int Isearchleft(int p,int a,int b,int t,String photo,int total)
	{
		int photos=0;
		if(p==1)
			return photos;
		if(photo.charAt(p-1)== 'w')
			total+=b;
		total+=obs;
		if(total<=t)
			photos++;
		total+=a;
		if(total>=t)
			return photos;
		else
		{
			return photos + Isearchleft(p-1,a,b,t,photo,total);
		}
	}
	public int Isearchright(int p,int a,int b,int t,String photo,int m,int total)
	{
		int photos=0;
		if(m==p)
			return photos;
		if(photo.charAt(m)== 'w')
			total+=b;
		total+=obs;
		if(total<=t)
			photos++;
		total+=a;
		if(total>=t)
			return photos;
		else
		{
			return photos + Isearchright(p,a,b,t,photo,m+1,total);
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sn = new Scanner(System.in);
		Solution sl = new Solution();
		int p =sn.nextInt();
		int a = sn.nextInt();
		int b = sn.nextInt();
		int t = sn.nextInt();
		String gallery = sn.next();
		int total=0;
		int fl = sl.Isearch(p,a,b,t,gallery,total);
		System.out.println(fl);
		sn.close();
	}

}
