#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int cutpaper(int n, int m)
 {
    if(n==1 && m==1)
        return 0;
    else if(n==1)
        return m-1;
    else if(m==1)
        return n-1;
    else 
       { return (cutpaper(n,1)+cutpaper(n,m-1)+1);
       }
          
           
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n,m,cuts=0;
    cin>>n>>m;
    int k=cutpaper(n,m);
    cout<<k<<"\n";
    return 0;
}