//Linkwish's code
#include<bits/stdc++.h>
#include "richest.h"
#define endl '\n'
#define si static inline
#define mp make_pair
#define fi first
#define se second
using namespace std;typedef long long ll;typedef __int128 li;
typedef pair<int,int> pii;typedef pair<ll,ll> pll;typedef const int ci;
typedef const ll cl;const int iinf=INT_MAX;const ll linf=LLONG_MAX;
template<typename T>si bool gmax(T &x,const T y){if(x<y)return x=y,1;return 0;}
template<typename T>si bool gmin(T &x,const T y){if(y<x)return x=y,1;return 0;}

int n;

namespace S1{
	ci N=1005;
	int tot[N];
	si int solve(){
		memset(tot,0,sizeof tot);
		vector<int> a,b;
		for(int i=0;i<n;i++)
			for(int j=i+1;j<n;j++)
				a.push_back(i),b.push_back(j);
		vector<int> res=ask(a,b);
		for(int i=0;i<(int)res.size();i++)tot[res[i]]++;
		for(int i=0;i<n;i++)if(tot[i]==n-1)return i;
		return -1;
	}
}
namespace S2{
	


	si int solve(){
		vector<int> cur;
		for(int i=0;i<n;i++)cur.push_back(i);
		mt19937 R(chrono::high_resolution_clock().now().time_since_epoch().count());
		while(cur.size()>1){
			//cerr<<"IN "<<cur.size()<<endl;
			shuffle(cur.begin(),cur.end(),R);
			vector<int> a,b;
			for(int i=0;i<(int)cur.size()-1;i++)a.push_back(cur[i]),b.push_back(cur[i+1]);
			vector<int> res=ask(a,b),tmp;
			for(int i=0;i<(int)res.size();){
				if(res[i]==cur[i]){
					tmp.push_back(cur[i]);
					int j=i+1;
					while(j<(int)res.size()&&cur[j]==res[j])j++;
					i=j;
				}
				else{
					int j=i+1;
					while(j<(int)cur.size()&&cur[j]==res[j-1])j++;
					tmp.push_back(cur[j-1]);
					i=j;
				}
			}
			cur.swap(tmp);
		}
		return cur[0];
	}
}
int richest(int N, int T, int S) {
	n=N;
	if(N<=1000)return S1::solve();
	else return S2::solve();
    return -1;
}