Little X and Little Z are good friends. They always chat online. But both of them have schedules.

Little Z has fixed schedule. He always online at any moment of time between a1 and b1, between a2 and b2, ..., between ap and bp (all borders inclusive). But the schedule of Little X is quite strange, it depends on the time when he gets up. If he gets up at time 0, he will be online at any moment of time between c1 and d1, between c2 and d2, ..., between cq and dq (all borders inclusive). But if he gets up at time t, these segments will be shifted by t. They become [ci + t, di + t] (for all i).

If at a moment of time, both Little X and Little Z are online simultaneosly, they can chat online happily. You know that Little X can get up at an integer moment of time between l and r (both borders inclusive). Also you know that Little X wants to get up at the moment of time, that is suitable for chatting with Little Z (they must have at least one common moment of time in schedules). How many integer moments of time from the segment [l, r] suit for that?

Input

The first line contains four space-separated integers p, q, l, r (1 ≤ p, q ≤ 50; 0 ≤ l ≤ r ≤ 1000).

Each of the next p lines contains two space-separated integers ai, bi (0 ≤ ai < bi ≤ 1000). Each of the next q lines contains two space-separated integers cj, dj (0 ≤ cj < dj ≤ 1000).

It's guaranteed that bi < ai + 1 and dj < cj + 1 for all valid i and j.

Output

Output a single integer — the number of moments of time from the segment [l, r] which suit for online conversation.

Examples

Input

1 1 0 4
2 3
0 1


Output

3


Input

2 3 0 20
15 17
23 26
1 4
7 11
15 17


Output

20
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Scanner;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.util.InputMismatchException;

/**
 * Ashesh Vidyut (Drift King) *
 */
public class B {
    public static void main(String[] args) {
        try {
            InputReader in = new InputReader(System.in);
            BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));
            int p = in.readInt();
            int q = in.readInt();
            int l = in.readInt();
            int r = in.readInt();
            int zsch[][] = new int[p][2];
            int zshf[] = new int[p];
            for (int i = 0; i < p; i++) {
                int ai = in.readInt();
                int bi = in.readInt();
                zsch[i][0] = ai;
                zsch[i][1] = bi;
                zshf[i] = ai;
            }
            int xsch[][] = new int[q][2];
            for (int i = 0; i < q; i++) {
                int ci = in.readInt();
                int di = in.readInt();
                xsch[i][0] = ci;
                xsch[i][1] = di;
            }
            int ans = 0;
            for (int i = l; i <= r; i++) {
                int xschnew[][] = new int[q][2];
                for (int j = 0; j < q; j++) {
                    xschnew[j][0] = xsch[j][0] + i;
                    xschnew[j][1] = xsch[j][1] + i;
                }
                boolean gotone = false;
                for (int j = 0; j < p && !gotone; j++) {
                    for (int k = 0; k < q; k++) {
                        if(commonMoment(xschnew[k], zsch[j])){
                            ans++;
                            gotone = true;
                            break;
                        }
                    }
                }
            }
            out.write(Integer.toString(ans));
            out.newLine();
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static boolean commonMoment(int a[], int b[]){
        if(a[0] == b[0])
            return true;
        if(a[1] == b[1])
            return true;
        if(a[0] < b[0]){
            if(a[1] >= b[0]){
                return true;
            }
            return false;
        }
        else{
            if(b[1] >= a[0]){
                return true;
            }
            return false;
        }
    }
}
class InputReader {
    private boolean finished = false;

    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;

    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 peek() {
        if (numChars == -1)
            return -1;
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                return -1;
            }
            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 long readLong() {
        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 readString() {
        int length = readInt();
        if (length < 0)
            return null;
        byte[] bytes = new byte[length];
        for (int i = 0; i < length; i++)
            bytes[i] = (byte) read();
        try {
            return new String(bytes, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            return new String(bytes);
        }
    }

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

    private String readLine0() {
        StringBuffer buf = new StringBuffer();
        int c = read();
        while (c != '\n' && c != -1) {
            if (c != '\r')
                buf.appendCodePoint(c);
            c = read();
        }
        return buf.toString();
    }

    public String readLine() {
        String s = readLine0();
        while (s.trim().length() == 0)
            s = readLine0();
        return s;
    }

    public String readLine(boolean ignoreEmptyLines) {
        if (ignoreEmptyLines)
            return readLine();
        else
            return readLine0();
    }

    public BigInteger readBigInteger() {
        try {
            return new BigInteger(readString());
        } catch (NumberFormatException e) {
            throw new InputMismatchException();
        }
    }

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

    public double readDouble() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        double res = 0;
        while (!isSpaceChar(c) && c != '.') {
            if (c == 'e' || c == 'E')
                return res * Math.pow(10, readInt());
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res *= 10;
            res += c - '0';
            c = read();
        }
        if (c == '.') {
            c = read();
            double m = 1;
            while (!isSpaceChar(c)) {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, readInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                m /= 10;
                res += (c - '0') * m;
                c = read();
            }
        }
        return res * sgn;
    }

    public boolean isExhausted() {
        int value;
        while (isSpaceChar(value = peek()) && value != -1)
            read();
        return value == -1;
    }

    public String next() {
        return readString();
    }

    public boolean readBoolean() {
        return readInt() == 1;
    }
}

