1 #include<iostream> 2 using namespace std; 3  4 const int maxn = 100000 + 5; 5  6 int p[maxn]; 7  8 int find(int x) 9 {10     return p[x] != x ? p[x] = (find(p[x])) : x;11 }12 13 int main()14 {15     //freopen("D:\\txt.txt", "r", stdin);16     int x, y;17     while (cin >> x && x != -1)18     {19         for (int i = 0; i < maxn; i++)20             p[i] = i;21         int cnt = 0;22         while (x != -1)23         {24             cin >> y;25             x = find(x);26             y = find(y);27             if (x == y)   cnt++;28             else p[x] = y;29             cin >> x;30         }31         cout << cnt << endl;32     }33 }