#include<cstdio>
#include<cstring>
#include<cassert>
#include<vector>
#include<list>
#include<queue>
#include<map>
#include<set>
#include<deque>
#include<stack>
#include<bitset>
#include<algorithm>
#include<functional>
#include<numeric>
#include<utility>
#include<sstream>
#include<iostream>
#include<iomanip>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<fstream>
#include<typeinfo>
#include<locale>
#include<iterator>
#include<valarray>
#include<complex>
using namespace std;

int main()
{
    int n,m;

    while(cin>>n>>m){
        int sum = 0,flag = 0,count = -1,x=n*m;
        n--;
        if(n==0 || m==0){
            cout<<"0"<<endl;
            continue;
        }
        while(sum < x){
            if(flag==0){
                sum += m;
                flag = 1;
                m--;
            }
            else if(flag==1){
                sum += n;
                flag = 0;
                n--;
            }
            count++;
        }
        cout<<count<<endl;
    }

    return 0;
}

here is my code, it has got verdict WA in test case 10....