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

int main() {

    long n,m;
    scanf("%ld %ld",&n,&m);
    if(n==1&&m==1)printf("0");
    else if(n==1&&m>1)printf("%ld",m-1);
    else if(n>1&&m==1)printf("%ld",n-1);
        else printf("%lld",(long long)(m*n)-1);
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}