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

public class MainClass
{
    public static void main(String[] args)throws IOException
    {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String s1[] = in.readLine().split(" ");
        int n = Integer.parseInt(s1[0]);
        long a = Long.parseLong(s1[1]);
        long b = Long.parseLong(s1[2]);
        long t = Long.parseLong(s1[3]);
        char[] S = in.readLine().toCharArray();
        long[] time = new long[n];
        for (int i=n - 1;i>=0;i--)
        {
            if (S[i] == 'w')
            {
                time[i] += b + 1;
            }
            else
                time[i] += 1;
            if (i != n - 1)
                time[i] += time[i + 1];
        }
        long[] ti = new long[n];
        for (int i=0;i<n;i++)
        {
            if (S[i] == 'w')
                ti[i] += b + 1;
            else
                ti[i] ++;
            if (i > 0)
                ti[i] += ti[i - 1];
        }
        int l = 0;
        int r = n;
        int ans = 0;
        while (l <= r)
        {
            int mid = (l + r) / 2;
            if (check(a, b, t, mid, S, ti, time))
            {
                ans = mid;
                l = mid + 1;
            }
            else
                r = mid - 1;
        }
        System.out.println(ans);
    }
    public static boolean check(long a, long b, long t, int mid, char[] S, long[] ti, long[] time)
    {
        int n = S.length;
        for (int i=1;i<=mid;i++)
        {
            int right = mid - i;
            long sum = 0L;
            if (right > 0)
            {
                sum += time[n - right];
            }
            sum += ti[i - 1];
            if (right == 0)
                sum += (i - 1) * a;
            else
            {
                long sum1 = sum;
                long sum2 = sum;
                sum1 += 2 * (i - 1) * a + right * a;
                sum2 += 2 * right * a + (i - 1) * a;
                sum = Math.min(sum1, sum2);
            }
            if (sum <= t)
                return true;
        }
        return false;
    }
}
class Reader
{
    final private int BUFFER_SIZE = 1 << 16;
    private DataInputStream din;
    private byte[] buffer;
    private int bufferPointer, bytesRead;

    public Reader()
    {
        din = new DataInputStream(System.in);
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public Reader(String file_name) throws IOException
    {
        din = new DataInputStream(new FileInputStream(file_name));
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public String readLine() throws IOException
    {
        byte[] buf = new byte[64]; // line length
        int cnt = 0, c;
        while ((c = read()) != -1)
        {
            if (c == '\n')
                break;
            buf[cnt++] = (byte) c;
        }
        return new String(buf, 0, cnt);
    }

    public int nextInt() throws IOException
    {
        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 long nextLong() throws IOException
    {
        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 double nextDouble() throws IOException
    {
        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() throws IOException
    {
        if (bufferPointer == bytesRead)
            fillBuffer();
        return buffer[bufferPointer++];
    }

    public void close() throws IOException
    {
        if (din == null)
            return;
        din.close();
    }
}