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

int main() {

    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    long long int n,m,resh=0,resv=0,sum=0;
    scanf("%lld %lld",&n,&m);
    if(n==1 && m==1)
        printf("0");
    else if(n==1)
        printf("%lld",m-1);
    else if(m==1)
        printf("%lld",n-1);
    else
        {
            resh = n-1;
            sum = resh;
            resv = n*(m-1);
            sum+=resv;
            printf("%lld",sum);
    }

    return 0;
}