In one one-dimensional world there are n platforms. Platform with index k (platforms are numbered from 1) is a segment with coordinates [(k - 1)m, (k - 1)m + l], and l < m. Grasshopper Bob starts to jump along the platforms from point 0, with each jump he moves exactly d units right. Find out the coordinate of the point, where Bob will fall down. The grasshopper falls down, if he finds himself not on the platform, but if he finds himself on the edge of the platform, he doesn't fall down.

Input

The first input line contains 4 integer numbers n, d, m, l (1 ≤ n, d, m, l ≤ 106, l < m) — respectively: amount of platforms, length of the grasshopper Bob's jump, and numbers m and l needed to find coordinates of the k-th platform: [(k - 1)m, (k - 1)m + l].

Output

Output the coordinates of the point, where the grosshopper will fall down. Don't forget that if Bob finds himself on the platform edge, he doesn't fall down.

Examples

Input

2 2 5 3


Output

4


Input

5 4 11 8


Output

20
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Locale;
import java.util.Scanner;
import java.util.regex.Pattern;

import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;

public class Main {

	public static void main(String[] args) throws Exception {
        solve(1);	
    }
     
    public static void solve(int testCases) throws Exception{
    	int n = StdIn.readInt();
    	long d = StdIn.readLong();
    	long m = StdIn.readLong();
    	long l = StdIn.readLong();
    	Platform[] p = new Platform[n + 1];
    	for(int i = 1 ; i <= n ; i++){
    		long a = (i - 1) * m ;
    		long b = a + l;
    		p[i] = new Platform(a, b);
    	}
    	
    	long point = 0;
    	
    	for(int i = 1 ; i <= n ; i++){
    		
    		if(p[i].isInside(point)){
    			long q = (p[i].getRight() - point) / d;
    			point += (q + 1) * d;
    		}
    		
    	}
    	StdOut.println(point);
    }       
}

class Platform{
	private long left;
	private long right;
	public Platform(long a, long b){
		left = a;
		right = b;
	}
	public long getLeft(){return left;}
	public long getRight(){return right;}
	public boolean isInside(long p){return p >= getLeft() && p <= getRight();}
	public String toString(){return "[" + getLeft() + "," + getRight() + "]";}
}


final class StdIn {
 
    private StdIn() { }
 
    private static Scanner scanner;
    
    private static final String CHARSET_NAME = "UTF-8";
 
    private static final Locale LOCALE = Locale.US;
 
    private static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\p{javaWhitespace}+");
 
    private static final Pattern EMPTY_PATTERN = Pattern.compile("");
 
    private static final Pattern EVERYTHING_PATTERN = Pattern.compile("\\A");
 
    public static boolean isEmpty() {
        return !scanner.hasNext();
    }
 
    public static boolean hasNextLine() {
        return scanner.hasNextLine();
    }
 
    public static boolean hasNextChar() {
        scanner.useDelimiter(EMPTY_PATTERN);
        boolean result = scanner.hasNext();
        scanner.useDelimiter(WHITESPACE_PATTERN);
        return result;
    }
 
    public static String readLine() {
        String line;
        try                 { line = scanner.nextLine(); }
        catch (Exception e) { line = null;               }
        return line;
    }
 
    public static char readChar() {
        scanner.useDelimiter(EMPTY_PATTERN);
        String ch = scanner.next();
        assert (ch.length() == 1) : "Internal (Std)In.readChar() error!"
            + " Please contact the authors.";
        scanner.useDelimiter(WHITESPACE_PATTERN);
        return ch.charAt(0);
    }  
 
 
    public static String readAll() {
        if (!scanner.hasNextLine())
            return "";
 
        String result = scanner.useDelimiter(EVERYTHING_PATTERN).next();
        // not that important to reset delimeter, since now scanner is empty
        scanner.useDelimiter(WHITESPACE_PATTERN); // but let's do it anyway
        return result;
    }
 
    public static String readString() {
        return scanner.next();
    }
 
    public static int readInt() {
        return scanner.nextInt();
    }
 
    public static double readDouble() {
        return scanner.nextDouble();
    }
 
    public static float readFloat() {
        return scanner.nextFloat();
    }
 
    public static long readLong() {
        return scanner.nextLong();
    }
    
    public static short readShort() {
        return scanner.nextShort();
    }
 
    public static byte readByte() {
        return scanner.nextByte();
    }
 
    public static boolean readBoolean() {
        String s = readString();
        if (s.equalsIgnoreCase("true"))  return true;
        if (s.equalsIgnoreCase("false")) return false;
        if (s.equals("1"))               return true;
        if (s.equals("0"))               return false;
        throw new InputMismatchException();
    }
 
    public static String[] readAllStrings() {
        // we could use readAll.trim().split(), but that's not consistent
        // because trim() uses characters 0x00..0x20 as whitespace
        String[] tokens = WHITESPACE_PATTERN.split(readAll());
        if (tokens.length == 0 || tokens[0].length() > 0)
            return tokens;
 
        // don't include first token if it is leading whitespace
        String[] decapitokens = new String[tokens.length-1];
        for (int i = 0; i < tokens.length - 1; i++)
            decapitokens[i] = tokens[i+1];
        return decapitokens;
    }
 
    public static String[] readAllLines() {
        ArrayList<String> lines = new ArrayList<String>();
        while (hasNextLine()) {
            lines.add(readLine());
        }
        return lines.toArray(new String[0]);
    }
 
    public static int[] readAllInts() {
        String[] fields = readAllStrings();
        int[] vals = new int[fields.length];
        for (int i = 0; i < fields.length; i++)
            vals[i] = Integer.parseInt(fields[i]);
        return vals;
    }
 
    public static double[] readAllDoubles() {
        String[] fields = readAllStrings();
        double[] vals = new double[fields.length];
        for (int i = 0; i < fields.length; i++)
            vals[i] = Double.parseDouble(fields[i]);
        return vals;
    }
    
    static {
        resync();
    }
 
    private static void resync() {
        setScanner(new Scanner(new java.io.BufferedInputStream(System.in), CHARSET_NAME));
    }
    
    private static void setScanner(Scanner scanner) {
        StdIn.scanner = scanner;
        StdIn.scanner.useLocale(LOCALE);
    }
 
    public static int[] readInts() {
        return readAllInts();
    }
 
    public static double[] readDoubles() {
        return readAllDoubles();
    }
 
    public static String[] readStrings() {
        return readAllStrings();
    }
 
}
 
final class StdOut {
 
    private static final String CHARSET_NAME = "UTF-8";
 
    private static final Locale LOCALE = Locale.US;
 
    private static PrintWriter out;
 
    static {
        try {
            out = new PrintWriter(new OutputStreamWriter(System.out, CHARSET_NAME), true);
        }
        catch (UnsupportedEncodingException e) { System.out.println(e); }
    }
 
    private StdOut() { }
 
    public static void close() {
        out.close();
    }
 
    public static void println() {
        out.println();
    }
 
    public static void println(Object x) {
        out.println(x);
    }
 
    public static void println(boolean x) {
        out.println(x);
    }
 
    public static void println(char x) {
        out.println(x);
    }
 
    public static void println(double x) {
        out.println(x);
    }
 
    public static void println(float x) {
        out.println(x);
    }
 
    public static void println(int x) {
        out.println(x);
    }
 
    public static void println(long x) {
        out.println(x);
    }
 
    public static void println(short x) {
        out.println(x);
    }
 
    public static void println(byte x) {
        out.println(x);
    }
 
    public static void print() {
        out.flush();
    }
 
    public static void print(Object x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(boolean x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(char x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(double x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(float x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(int x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(long x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(short x) {
        out.print(x);
        out.flush();
    }
 
    public static void print(byte x) {
        out.print(x);
        out.flush();
    }
 
    public static void printf(String format, Object... args) {
        out.printf(LOCALE, format, args);
        out.flush();
    }
 
    public static void printf(Locale locale, String format, Object... args) {
        out.printf(locale, format, args);
        out.flush();
    }
 
}