Language: C++

#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;

//#define int long long
using bll = boost::multiprecision::cpp_int;
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
#ifdef LOCAL_ENV
	#define debug(var) std::cout<<#var" = "<<var<<std::endl
#else
	#define debug(var)
#endif
#define p(var) std::cout<<var<<std::endl
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define all(a) (a).begin(), (a).end()
#define PI (acos(-1))
template<typename T> inline T power(T x, T n){ return n ? power(x*x%MOD,n/2)*(n%2?x:1)%MOD : 1; }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T1, typename T2>inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2>inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template<typename T1, typename T2> ostream& operator<<(ostream& s, const pair<T1, T2>& p) {return s << "(" << p.first << ", " << p.second << ")";}
template<typename T> ostream& operator<<(ostream& s, const vector<T>& v) {
	for (int i = 0, len = v.size(); i < len; ++i){
		s << v[i]; if (i < len - 1) s << "\t";
	}
	return s;
}
template<typename T> ostream& operator<<(ostream& s, const vector< vector<T> >& vv) {
	for (int i = 0, len = vv.size(); i < len; ++i){
		s << vv[i] << endl;
	}
	return s;
}
template<typename T1, typename T2> ostream& operator<<(ostream& s, const map<T1, T2>& m) {
	s << "{" << endl;
	for (typeof(m.begin()) itr = m.begin(); itr != m.end(); ++itr){
		s << "\t" << (*itr).first << " : " << (*itr).second << endl;
	}
	s << "}" << endl;
	return s;
}

/*-----8<-----8<-----*/

signed main() {
	std::chrono::system_clock::time_point  starttime, endtime;
	starttime = std::chrono::system_clock::now();

	scanf("%lld", &N);
	vector<vector<ll>> a(N, vector<ll>(N-1, 0));

	rep(i, N) rep(j, N-1) {
		ll t;
		scanf("%lld", &t);
		a[i][j]=t-1;
	}

	ll ans=0;
	vector<ll> index(N,0);
	while(1){
		endtime = std::chrono::system_clock::now();
		double elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(endtime - starttime).count();
		if(elapsed>1980){
			p(N*(N-1)/2);
			exit(0);
		}
		map<pair<ll,ll>,ll> m;
		rep(i,N){
			if(index[i]==N-1)continue;
			ll t=i,s=a[i][index[i]];
			if(s>t)swap(s,t);
			m[make_pair(s,t)]++;
		}

		bool gotonext=false;
		debug(m);
		debug(index);
		for(auto p:m){
			if(p.second!=2)continue;
			gotonext=true;
			index[p.first.first]++;
			index[p.first.second]++;
		}

		if(!gotonext){break;}
		ans++;
	}

	rep(i,N){
		if(index[i]!=N-1){
			p(-1);
			return 0;
		}
	}

	printf("%lld\n", ans);
	return 0;
}


Compiler output:
a.cc:2:10: fatal error: boost/multiprecision/cpp_int.hpp: No such file or directory
    2 | #include <boost/multiprecision/cpp_int.hpp>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.