#include<iostream>
#include<cstdio>
using namespace std;

int main()
{
	int n,a,i=0;
	scanf("%d",&n);
	while(scanf("%d",&a)==1)
		i++;
	if((n-1)*2!=i)
		while(1);
	return 0;
}

这个会OLE
#include<iostream>
#include<cstdio>
using namespace std;

int main()
{
	int n,a,i=0;
	scanf("%d",&n);
	while(scanf("%d",&a)==1)
		i++;
	if((n-1)*2!=i)
		while(1)
                   cout<<"shfushfu"<<endl;
	return 0;
}