#include "bits/stdc++.h" using namespace std; typedef long long ll; typedef unsigned long long ull; typedef vector veci; typedef vector vecll; typedef vector vecs; template using Hash=unordered_map; #define REP(i, a, n) for(ll i = a; i < (ll)(n); i++) #define RREP(i, a, n) for(ll i = n-1; i >= (ll)(a); i--) #define rep(i, n) REP(i, 0, n) #define rrep(i, n) RREP(i, 0, n) #define MD 1000000007 #define _SPLIT " " template T read(){T a;cin >> a;return a;} template void read(T& a){cin >> a;} template void read(T& a, Args&... args){cin >> a; read(args...);} template void rarr(T a, int n){for(int i = 0; i < n; i++) {cin >> a[i];}} template void write(T a){cout << setprecision(12) << a << endl;} template void write(T a, Args... args){cout << setprecision(12) << a << _SPLIT; write(args...);} template void warr(vector a, const char* c = " "){cout << a[0];for(int i = 1; i < (int)a.size(); i++)cout << c << a[i];cout << endl;;} template void warr(T a, int n, const char* c = " "){cout << a[0];for(int i = 1; i < n; i++)cout << c << a[i];cout << endl;} void split(string s, string delim, veci& result){result.clear();string::size_type pos = 0;while(pos != string::npos){string::size_type p = s.find(delim, pos);if(p == string::npos){result.push_back(atoi(s.substr(pos).data()));break;}else {result.push_back(atoi(s.substr(pos, p - pos).data()));}pos = p + delim.size();}} void split(string s, string delim, vecs& result){result.clear();string::size_type pos = 0;while(pos != string::npos){string::size_type p = s.find(delim, pos);if(p == string::npos){result.push_back(s.substr(pos));break;}else {result.push_back(s.substr(pos, p - pos));}pos = p + delim.size();}} ll gcd(ll a, ll b){while(true){ll k = a % b;if(k == 0)return b;a = b;b = k;}} ll comb(ll n, ll m){ll p=1;m=min(m,n-m);for(ll i=1;i<=m;i++){p*=n-i+1;p/=i;}return p;} typedef int Weight; struct Edge { int src, dst; Weight weight; Edge(int src, int dst, Weight weight=1) : src(src), dst(dst), weight(weight) { } }; bool operator < (const Edge &e, const Edge &f) { return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!! e.src != f.src ? e.src < f.src : e.dst < f.dst; } typedef vector Edges; typedef vector Graph; typedef vector Array; typedef vector Matrix; bool augment(const Graph& g, int u, vector& matchTo, vector& visited) { if (u < 0) return true; for(auto& e:g[u]) if (!visited[e.dst]) { visited[e.dst] = true; if (augment(g, matchTo[e.dst], matchTo, visited)) { matchTo[e.src] = e.dst; matchTo[e.dst] = e.src; return true; } } return false; } int bipartiteMatching(const Graph& g, int L, Edges& matching) { const int n = g.size(); vector matchTo(n, -1); int match = 0; rep(u, L) { vector visited(n); if (augment(g, u, matchTo, visited)) ++match; } rep(u, L) if (matchTo[u] >= 0) // make explicit matching matching.push_back( Edge(u, matchTo[u]) ); return match; } int main(void) { int n; read(n); Graph g(2*n); rep(i,n){ int a; read(a); rep(j,n)if(a!=j) g[i].push_back(Edge(i,j+n)), g[j+n].push_back(Edge(j+n,i)); } Edges e; int m_num=bipartiteMatching(g,n,e); if(m_num