import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader in = new FastReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        BImagePreview solver = new BImagePreview();
        solver.solve(1, in, out);
        out.close();
    }

    static class BImagePreview {
        public void solve(int testNumber, FastReader s, PrintWriter out) {
            int n = s.nextInt();
            long a = s.nextLong();
            long b = s.nextLong();
            long t = s.nextLong();
            String str = s.nextString();
            long[] wFromBeg = new long[n];
            long[] wFromEnd = new long[n];

            for (int i = 0; i < n; i++) {
                if (str.charAt(i) == 'w') {
                    if (i == 0) {
                        wFromBeg[i]++;
                    } else {
                        wFromBeg[i] = wFromBeg[i - 1] + 1L;
                    }
                } else {
                    if (i != 0) {
                        wFromBeg[i] = wFromBeg[i - 1];
                    }
                }
            }

            for (int i = n - 1; i >= 0; i--) {
                if (str.charAt(i) == 'w') {
                    if (i == n - 1) {
                        wFromEnd[i]++;
                    } else {
                        wFromEnd[i] = wFromEnd[i + 1] + 1L;
                    }
                } else {
                    if (i != n - 1) {
                        wFromEnd[i] = wFromEnd[i + 1];
                    }
                }
            }

            long left = 1;
            long right = n;
            long ans = 0;
            while (left <= right) {
                long currLen = (left + right) / 2L;
                boolean found = false;
                for (long i = currLen - 1; i >= 0; i--) {
                    long fromFront = i;
                    long fromBack = currLen - fromFront - 1;

                    int totalW = 0;
                    totalW += wFromBeg[(int) fromFront];
                    if (fromBack != 0) {
                        totalW += wFromEnd[(int) (n - fromBack)];
                    }

                    long totalH = currLen - totalW;
                    if (((2L * Math.min(fromFront, fromBack)) + (Math.max(fromFront, fromBack))) * a + totalH + totalW * (b + 1L) <= t) {
                        found = true;
                        break;
                    }
                }

                if (found) {
                    ans = Math.max(ans, currLen);
                    left = currLen + 1L;
                } else {
                    right = currLen - 1L;
                }
            }

            out.println(ans);
        }

    }

    static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private FastReader.SpaceCharFilter filter;

        public FastReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nextLong() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String nextString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
}

