
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    }
} import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    } main {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc int c = sc.nextInt(); c sc.nextInt() sc.nextInt sc int d = sc.nextInt(); d sc.nextInt() sc.nextInt sc int count = 0; count 0 for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		} int i = a; int i = a; i a i <= b i b i++ i++ i {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		} {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		} for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			} int j = c; int j = c; j c j <= d j d j++ j++ j {
				if (i == j) {
					count++;
					break;
				}
			} {
				if (i == j) {
					count++;
					break;
				}
			} if (i == j) {
					count++;
					break;
				} i == j i j {
					count++;
					break;
				} count++ count break; if (count > 0) {
        	count--;
        } count > 0 count 0 {
        	count--;
        } count-- count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    }
} Main

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        
        int count = 0;
        for (int i = a; i <= b; i++) {
			for (int j = c; j <= d; j++) {
				if (i == j) {
					count++;
					break;
				}
			}
		}
        
        if (count > 0) {
        	count--;
        }
        
        System.out.println(count);
    }
}