import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
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;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskD solver = new TaskD();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskD {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            long a = in.readInt();
            long b = in.readInt();
            long t = in.readInt();
            Photo[] photos = new Photo[n];
            for (int i = 0; i < n; i++) {
                photos[i] = new Photo(in.readCharacter());
            }
            Photo[] newPhotos = new Photo[n];
            newPhotos[0] = photos[0];
            for (int i = 1; i < n; i++) {
                newPhotos[i] = photos[n - i];
            }

            Solver mySolver1 = new MySolver(n, a, b, t, photos);
            Solver mySolver2 = new MySolver(n, a, b, t, newPhotos);

            Solver naiveSolver1 = new NaiveSolver(n, a, b, t, photos);
            Solver naiveSolver2 = new NaiveSolver(n, a, b, t, newPhotos);

            out.print(Math.max(mySolver1.solve(), mySolver2.solve()));
        }

    }

    static class NaiveSolver extends Solver {
        NaiveSolver(int n, long a, long b, long t, Photo[] photos) {
            super(n, a, b, t, photos);
        }


        public long solve() {
            long ans = 0;
            long usedTime = 0;
            for (int i = 0; i < n; i++) {
                if (i > 0) {
                    usedTime += a;
                }
                usedTime += photos[i].orientation * b + 1;

                long leftTime = t - usedTime;
                if (leftTime >= 0) {
                    ans = Math.max(ans, i + 1);
                }

                if (leftTime >= 0) {
                    leftTime -= i * a;
                    int addedPhotos = 0;
                    while (addedPhotos + i + 1 < n) {
                        int curPhotoIdx = n - addedPhotos - 1;
                        leftTime -= a + 1;
                        leftTime -= photos[curPhotoIdx].orientation * b;
                        if (leftTime >= 0) {
                            addedPhotos++;
                        } else {
                            break;
                        }
                    }
                    ans = Math.max(ans, i + 1 + addedPhotos);
                }
            }

            return Math.min(n, ans);
        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void print(long i) {
            writer.print(i);
        }

    }

    static class Photo {
        final int orientation;

        Photo(char orientation) {
            this.orientation = orientation == 'h' ? 0 : 1;
        }


        public String toString() {
            return "Photo{" +
                    "orientation=" + orientation +
                    '}';
        }

    }

    static class MySolver extends Solver {
        MySolver(int n, long a, long b, long t, Photo[] photos) {
            super(n, a, b, t, photos);
        }


        public long solve() {
            long[] toLeft = new long[n];
            for (int i = 2; i < n; i++) {
                toLeft[i] += toLeft[i - 1] + a + 1;
                toLeft[i] += photos[n - i].orientation * b;
            }

            long ans = 0;
            long usedTime = 0;
            for (int i = 0; i < n; i++) {
                if (i > 0) {
                    usedTime += a;
                }
                usedTime += photos[i].orientation * b + 1;

                long leftTime = t - usedTime;
                if (leftTime >= 0) {
                    ans = Math.max(ans, i + 1);
                }

                leftTime -= (i + 1) * a + 1 + photos[n - 1].orientation * b;
                if (leftTime >= 0) {
                    ans = Math.max(ans, i + 2);

                    int gotToLeft = Arrays.binarySearch(toLeft, leftTime);
                    if (gotToLeft < 0) {
                        gotToLeft = (~gotToLeft) - 1;
                    }
                    ans = Math.max(ans, i + 1 + gotToLeft);
                }
            }

            return Math.min(n, ans);
        }

    }

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

        public InputReader(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 readInt() {
            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 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 char readCharacter() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            return (char) c;
        }

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

        }

    }

    static abstract class Solver {
        final int n;
        final long a;
        final long b;
        final long t;
        final Photo[] photos;

        Solver(int n, long a, long b, long t, Photo[] photos) {
            this.n = n;
            this.a = a;
            this.b = b;
            this.t = t;
            this.photos = photos;
        }

        public abstract long solve();

    }
}

