import java.io.*;
import java.util.*;

public class MainB {
	static final StdIn in = new StdIn();
	static final PrintWriter out = new PrintWriter(System.out);
	
	public static void main(String[] args) {
		int n=in.nextInt(), a=in.nextInt(), b=in.nextInt(), t=in.nextInt();
		char[] o = in.next().toCharArray();
		int ans=solve(n, a, b, t, o);
		for(int i=1; i<n-i; ++i) {
			o[i]^=o[n-i];
			o[n-i]^=o[i];
			o[i]^=o[n-i];
		}
		//out.println(o);
		ans=Math.max(solve(n, a, b, t, o), ans);
		out.println(ans);
		out.close();
	}
	
	static int solve(int n, int a, int b, int t, char[] o) {
		int[] ps = new int[n+1];
		ps[n]=0;
		for(int i=n-1; i>=0; --i)
			ps[i]=ps[i+1]+a+(o[i]=='w'?b:0)+1;
		int ans=0, used=-a;
		for(int i=0; i<n; ++i) {
			used+=a+(o[i]=='w'?b:0)+1;
			int lb=i+1, rb=n;
			while(lb<=rb) {
				int m=(lb+rb)/2;
				if(used+a*i+ps[m]<=t)
					rb=m-1;
				else
					lb=m+1;
			}
			if(used<=t)
				ans=Math.max(Math.max(i+1, i+1+n-lb), ans);
		}
		return ans;
	}
	
	static class StdIn {
		final private int BUFFER_SIZE = 1 << 16;
		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer, bytesRead;
		public StdIn() {
			din = new DataInputStream(System.in);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}
		public StdIn(InputStream in) {
			try{
				din = new DataInputStream(in);
			} catch(Exception e) {
				throw new RuntimeException();
			}
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}
		public String next() {
			int c;
			while((c=read())!=-1&&(c==' '||c=='\n'||c=='\r'));
			StringBuilder s = new StringBuilder();
			while (c != -1)
			{
				if (c == ' ' || c == '\n'||c=='\r')
					break;
				s.append((char)c);
				c=read();
			}
			return s.toString();
		}
		public String nextLine() {
			int c;
			while((c=read())!=-1&&(c==' '||c=='\n'||c=='\r'));
			StringBuilder s = new StringBuilder();
			while (c != -1)
			{
				if (c == '\n'||c=='\r')
					break;
				s.append((char)c);
				c = read();
			}
			return s.toString();
		}
		public int nextInt() {
			int ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do
				ret = ret * 10 + c - '0';
			while ((c = read()) >= '0' && c <= '9');

			if (neg)
				return -ret;
			return ret;
		}
		public int[] readIntArray(int n, int os) {
			int[] ar = new int[n];
			for(int i=0; i<n; ++i)
				ar[i]=nextInt()+os;
			return ar;
		}
		public long nextLong() {
			long ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do
				ret = ret * 10 + c - '0';
			while ((c = read()) >= '0' && c <= '9');
			if (neg)
				return -ret;
			return ret;
		}
		public long[] readLongArray(int n, long os) {
			long[] ar = new long[n];
			for(int i=0; i<n; ++i)
				ar[i]=nextLong()+os;
			return ar;
		}
		public double nextDouble() {
			double ret = 0, div = 1;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do
				ret = ret * 10 + c - '0';
			while ((c = read()) >= '0' && c <= '9');
			if (c == '.')
				while ((c = read()) >= '0' && c <= '9')
					ret += (c - '0') / (div *= 10);
			if (neg)
				return -ret;
			return ret;
		}
		private void fillBuffer() throws IOException {
			bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
			if (bytesRead == -1)
				buffer[0] = -1;
		}
		private byte read() {
			try{
				if (bufferPointer == bytesRead)
					fillBuffer();
				return buffer[bufferPointer++];
			} catch(IOException e) {
				throw new RuntimeException();
			}
		}
		public void close() throws IOException {
			if (din == null)
				return;
			din.close();
		}
	}
}