Please,Can anybody tell what is going wrong in my code of problem GUESS?

My solution:www.codechef.com/viewsolution/7500878

`//probability int main() { ll t,m,n,num,den,i,a,num1,num2; sl(t); while(t--) { scanf("%lld %lld",&m,&n); num1=((m+1)/2)*(n/2);//used braces! though not needed here! num2=(m/2)*((n+1)/2);//used braces! ,else value needed may change (m/2)*(n+1)/2 not same as (m/2)*((n+1)/2) num=num1+num2; den=n*m; a=gcd(num,den);//can also use inbuild __gcd() num/=a;den/=a; printf("%lld/%lld\n",num,den); } return 0; } `