#include<bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 4e7;
int head[maxn], tot, n, match[maxn], vis[maxn], cnt;
struct Edge {
	int v, to;
} e[maxn];
void addedge(int u, int v) {
	e[++tot] = {v, head[u]};
	head[u] = tot;
}
bool dfs(int u) {
	for (int p = head[u]; p; p = e[p].to) {
		int v = e[p].v;
		if (vis[v]) continue;
		vis[v] = true;
		if (!match[v] || dfs(match[v])) {
			match[v] = u;
			return true;
		}
	}
	return false;
}
signed main() {
	cin >> n;
	for (int i = 1, v1, v2 ; i <= n; i++) {
		cin >> v1 >> v2;
		addedge(v1, i);
		addedge(v2, i);
	}
	for (int i = 1; i <= n; i++) {
		if (!dfs(i)) {
			cout << i - 1 << endl;
			return 0;
		}
	}
	cout << n << endl;
	return 0;
}