import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;
import java.lang.*;
import java.math.*;


public class Main{
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        FasterScanner sc = new FasterScanner(System.in);
        FastPrinter printer = new FastPrinter();
        int p = sc.nextInt();
        int d = sc.nextInt();
        int m = sc.nextInt();
        int s = sc.nextInt();
        int count = 0;
        while(p>m) {
        	if(s<p) {
        		break;
        	}
        	s=s-p;
        	p=p-d;
        	count++;
        }
        if(p<=m)
        	count = count + s/m;
        System.out.println(count);
        printer.close();
        sc.close();
    }

    public class FasterScanner {
        private InputStream mIs;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;

        public FasterScanner() {
            this(System.in);
        }

        public FasterScanner(InputStream is) {
            mIs = is;
        }

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

        public String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        }

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

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

        public boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

        public void close() {
            try {
                mIs.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    class FastPrinter {
        PrintWriter writer;

        /**
         * Initialize the writer.
         */
        public FastPrinter() {
            writer = new PrintWriter(new BufferedOutputStream(System.out));
        }

        /**
         * Print the given String and add a newline.
         *
         * @param string
         *            The given String.
         */
        public void println(String string) {
            writer.println(string);
        }

        /**
         * Print the given String.
         *
         * @param string
         *            The given String.
         */
        public void print(String string) {
            writer.print(string);
        }

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