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

int main() {
   long int a,b;
    scanf("%ld%ld",&a,&b);
    long int count=0,ans;
    if(a%2!=0){
        ans=a-1;
    }
    else
        ans=a;
     printf("%ld",a*b-1);
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}