hdu acm-step 2.1.3 相遇周期

#include <cstdio>
#define ll long long
using namespace std;
ll gcd(ll a,ll b)
{
        ll r;
        while(b)
        {
                r = a%b;
                a = b;
                b = r;
        }
        return a;
}

ll lcm(ll a,ll b)
{
        return a*b/gcd(a,b);
}
int main()
{
        int T;
        scanf("%d",&T);
        while(T--)
        {
                ll a,b,c,d;
                scanf("%lld/%lld%lld/%lld",&a,&b,&c,&d);
                a = a*d;
                c = c*b;
                ll p = lcm(a,c);
                ll q = b*d;
                if(p%q == 0)printf("%lld\n",p/q);
                else{ll t = gcd(p,q);printf("%lld/%lld\n",p/t,q/t);};
        }
        return 0;
}