样例都过了，莫名其妙20

#include<bits/stdc++.h>
using namespace std;
int n,fz=0,fm=1;
int gcd(int a,int b)
{
	int r;
	if(a==0)return 1;
	while(a%b!=0)
	{
		r=a%b;
		a=b;
		b=r;
	}
	return b;
}
int main()
{
	cin>>n;
	while(n--)
	{
		int x,y,f;
		cin>>x>>y>>f;
		int t=fm;
		fz*=y,fm*=y;
		x*=t;
		if(f==1)
			fz+=x;
		else
			fz-=x;
		t=gcd(abs(fz),fm);
		fz/=t,fm/=t;
	}
	if(fz%fm==0) cout<<fz/fm;
	else cout<<fz<<'/'<<fm;
	return 0;
}