import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int m=sc.nextInt();
        int cut=0;
        if(m>n&&m>1)
            {
            if(n==1)
                {
                while(m>1)
                    {
                    cut++;
                    m--;
                }
            }
            else
                {
                while(n>1)
                    {
                    cut++;
                    n--;
                }
                   while(m>1)
                    {
                    cut++;
                    m--;
                }
            }
        }
        else if(n>m&&n>1)
            {
            if(m==1)
                {
                while(n>1)
                    {
                    cut++;
                    n--;
                }
            }
            else
                {
                while(n>1)
                    {
                    cut++;
                    n--;
                }
                   while(m>1)
                    {
                    cut++;
                    m--;
                }
            }
        }
            else
                {

            }
         
            
            
        
        System.out.println(cut);
}
}