import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N[] = new int[4]; N new int[4] 4 int ans1 = 0 ans1 0 ans2 = 0; ans2 0 for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 4 > i 4 i i++ i++ i {
            N[i] = sc.nextInt();
        } {
            N[i] = sc.nextInt();
        } N[i] = sc.nextInt() N[i] N i sc.nextInt() sc.nextInt sc if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        } N[0] > N[2] N[0] N 0 N[2] N 2 {
            ans1 = N[0];

        } ans1 = N[0] ans1 N[0] N 0 {
            ans1 = N[2];
        } ans1 = N[2] ans1 N[2] N 2 if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        } N[1] > N[3] N[1] N 1 N[3] N 3 {
            ans2 = N[3];
        } ans2 = N[3] ans2 N[3] N 3 {
            ans2 = N[1];
        } ans2 = N[1] ans2 N[1] N 1 if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        } ans1 > ans2 ans1 ans2 {
            System.out.println("0");
        } System.out.println("0") System.out.println System.out System System.out "0" {
            System.out.println(ans2 - ans1);
        } System.out.println(ans2 - ans1) System.out.println System.out System System.out ans2 - ans1 ans2 ans1 String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N[] = new int[4];
        int ans1 = 0, ans2 = 0;
        for (int i = 0; 4 > i; i++) {
            N[i] = sc.nextInt();
        }
        if (N[0] > N[2]) {
            ans1 = N[0];

        } else {
            ans1 = N[2];
        }
        if (N[1] > N[3]) {
            ans2 = N[3];
        } else {
            ans2 = N[1];
        }
        if (ans1 > ans2) {
            System.out.println("0");
        } else {
            System.out.println(ans2 - ans1);
        }
    }
}
