有判断分母为负数，但仍然WA #6 #7

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#include<iostream>
#include<cmath>
using namespace std;
long long g_c_d(long long a,long long b){
    while(a%b!=0){
        long long c=a%b;
        a=b;
        b=c;
    }
    return b;
}
long long l_c_m(long long a,long long b){
    return a*b/g_c_d(a,b);
}
signed main(){
    long long n,a,b,opt,ansa=0,ansb=0,l;
    cin>>n;
    cin>>a>>b>>opt;
    if(opt==1)ansa=a;
    else ansa=-a;
	ansb=b;
    for(int i=2;i<=n;i++){
        cin>>a>>b>>opt;
        if(opt==1){
            l=l_c_m(ansb,b);
            ansa=ansa*(l/ansb)+a*(l/b);
			ansb=b=l;
            
        }else{
            l=l_c_m(ansb,b);
            ansa=ansa*(l/ansb)-a*(l/b);
			ansb=l;
        }
    }
    l=g_c_d(ansa,ansb);
    ansa/=l;ansb/=l;
    if(ansb<0){
    	ansb=abs(b);
    	ansa=-a;
	}
    if(ansb==1) cout<<ansa;
    else cout<<ansa<<'/'<<ansb;
}