bzoj2935

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1005;
int fa[maxn], d[maxn], vis[maxn], sum[maxn];
int find(int x) {
    return x == fa[x] ? x : fa[x] = find(fa[x]);
}
int n, ans, a;
int main() {
    scanf("%d", &n);
    for(int i = 1; i < maxn; ++i) fa[i] = i;
    for(int i = 1; i <= n; ++i) {
        int x, y; scanf("%d%d", &x, &y);
        ++d[x];
        --d[y];
        vis[x] = vis[y] = 1;
        fa[find(x)] = find(y); 
    }
    for(int i = 1; i < maxn; ++i) 
        if(vis[i]) 
            sum[find(i)] += abs(d[i]);
    for(int i = 1; i < maxn; ++i) if(vis[i] && find(i) == i) {
        if(sum[i] == 0) ++a;
        else ans += sum[i];
    }
    printf("%d\n", ans / 2 + n + a);
    return 0;
}