#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

long int cuts(long int m,long int n){
   // int c;
    if(n==1)
    return m-1;    
    else
        {
       // c=n/2;
        return 1+cuts(m,n/2)+cuts(m,n-(n/2));
    }
    
}

int main() {
    long int m,n;
    scanf("%ld%ld",&m,&n);
   // int cut=cuts(m,n);
   
    if(m==1)
   { printf("%ld",n-1);return 0;}
        else if(n==1)
        { printf("%ld",m-1);return 0;}
   else printf("%ld",cuts(m,n));
   
    

    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}