import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.io.Closeable;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) throws Exception {
        Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 29);
        thread.start();
        thread.join();
    }

    static class TaskAdapter implements Runnable {
        @Override
        public void run() {
            InputStream inputStream = System.in;
            OutputStream outputStream = System.out;
            FastInput in = new FastInput(inputStream);
            FastOutput out = new FastOutput(outputStream);
            BImagePreview solver = new BImagePreview();
            solver.solve(1, in, out);
            out.close();
        }
    }

    static class BImagePreview {
        public void solve(int testNumber, FastInput in, FastOutput out) {
            int n = in.readInt();
            int a = in.readInt();
            int b = in.readInt();
            int t = in.readInt();
            int[] s = new int[n * 2];
            for (int i = 0; i < n; i++) {
                s[i] = s[i + n] = in.readChar() == 'w' ? b + 1 : 1;
            }

            t -= s[n];
            if (t < 0) {
                out.println(0);
                return;
            }

            int[] left = new int[n * 2];
            int[] right = new int[n * 2];

            for (int i = n - 1; i >= 1; i--) {
                left[i] = left[i + 1] + a + s[i];
            }
            for (int i = n + 1; i < 2 * n; i++) {
                right[i] = right[i - 1] + a + s[i];
            }
            int ans = 1;
            for (int i = 1; i < n; i++) {
                if (left[i] <= t) {
                    ans = Math.max(ans, n - i + 1);
                }
            }
            for (int i = n + 1; i < 2 * n; i++) {
                if (right[i] <= t) {
                    ans = Math.max(ans, i - n + 1);
                }
            }
            int r = n;
            int l = 1;
            while (left[l] > t) {
                l++;
            }
            for (int i = n + 1; i < 2 * n; i++) {
                r = i;
                while (r - l + 1 > n) {
                    l++;
                }
                while (l <= n && left[l] + right[r] + Math.min(n - l, r - n) * a > t) {
                    l++;
                }
                if (l > n) {
                    break;
                }
                ans = Math.max(ans, r - l + 1);
            }

            out.println(ans);
        }

    }

    static class FastInput {
        private final InputStream is;
        private byte[] buf = new byte[1 << 13];
        private int bufLen;
        private int bufOffset;
        private int next;

        public FastInput(InputStream is) {
            this.is = is;
        }

        private int read() {
            while (bufLen == bufOffset) {
                bufOffset = 0;
                try {
                    bufLen = is.read(buf);
                } catch (IOException e) {
                    bufLen = -1;
                }
                if (bufLen == -1) {
                    return -1;
                }
            }
            return buf[bufOffset++];
        }

        public void skipBlank() {
            while (next >= 0 && next <= 32) {
                next = read();
            }
        }

        public int readInt() {
            int sign = 1;

            skipBlank();
            if (next == '+' || next == '-') {
                sign = next == '+' ? 1 : -1;
                next = read();
            }

            int val = 0;
            if (sign == 1) {
                while (next >= '0' && next <= '9') {
                    val = val * 10 + next - '0';
                    next = read();
                }
            } else {
                while (next >= '0' && next <= '9') {
                    val = val * 10 - next + '0';
                    next = read();
                }
            }

            return val;
        }

        public char readChar() {
            skipBlank();
            char c = (char) next;
            next = read();
            return c;
        }

    }

    static class FastOutput implements AutoCloseable, Closeable, Appendable {
        private static final int THRESHOLD = 1 << 13;
        private final Writer os;
        private StringBuilder cache = new StringBuilder(THRESHOLD * 2);

        public FastOutput append(CharSequence csq) {
            cache.append(csq);
            return this;
        }

        public FastOutput append(CharSequence csq, int start, int end) {
            cache.append(csq, start, end);
            return this;
        }

        private void afterWrite() {
            if (cache.length() < THRESHOLD) {
                return;
            }
            flush();
        }

        public FastOutput(Writer os) {
            this.os = os;
        }

        public FastOutput(OutputStream os) {
            this(new OutputStreamWriter(os));
        }

        public FastOutput append(char c) {
            cache.append(c);
            afterWrite();
            return this;
        }

        public FastOutput append(int c) {
            cache.append(c);
            afterWrite();
            return this;
        }

        public FastOutput append(String c) {
            cache.append(c);
            afterWrite();
            return this;
        }

        public FastOutput println(int c) {
            return append(c).println();
        }

        public FastOutput println() {
            return append(System.lineSeparator());
        }

        public FastOutput flush() {
            try {
                os.append(cache);
                os.flush();
                cache.setLength(0);
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
            return this;
        }

        public void close() {
            flush();
            try {
                os.close();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        }

        public String toString() {
            return cache.toString();
        }

    }
}

