学步园

#include <cstdio>
#include <cstdlib>

const int MAXN(100010);

struct FIND_SET
{
	int fa[MAXN], rank[MAXN];
	void init(int n)
	{
		for(int i = 1; i <= n; ++i)
		{
			fa[i] = i;
			rank[i] = 1;
		}
	}
	int find(int sour)
	{
		return sour == fa[sour]? sour: fa[sour] = find(fa[sour]);
	}
	bool Union(int sour1, int sour2)
	{
		int fa1 = find(sour1);
		int fa2 = find(sour2);
		if(fa1 == fa2)
			return false;
		if(rank[fa1] >= rank[fa2])
		{
			rank[fa1] += rank[fa2];
			fa[fa2] = fa1;
		}
		else
		{
			rank[fa2] += rank[fa1];
			fa[fa1] = fa2;
		}
		return true;
	}
};

FIND_SET fs;

int main()
{
	while(true)
	{
		int A, B, ans(0);
		if(scanf("%d", &A) == EOF)
			break;
		fs.init(100000);
		while(A != -1)
		{
			scanf("%d", &B);
			if(!fs.Union(A, B))
				++ans;
			scanf("%d", &A);
		}
		printf("%d\n", ans);
	}
	return 0;
}