#include <bits/stdc++.h>
#include "popa.h"
#define all(v) (v).begin(), (v).end()
#define sortv(v) sort(all(v))
#define uniqv(v) (v).erase(unique(all(v)), (v).end())
#define pb push_back
#define FI first
#define SE second
#define lb lower_bound
#define ub upper_bound
#define mp make_pair
#define test 1
#define TEST if(test)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
const int MOD = 1000000007; // 998244353
const int INF = 2e9;
const ll INFLL = 1e18;
const int MAX_N = 1000;
/*
int query(int x, int y, int z, int w){
printf("%d %d %d %d", x, y, z, w);
int ret;
scanf("%d", &ret);
return ret;
}*/
vector<int> v;
int solve(int N, int* Left, int* Right){
int r = 0;
Left[0] = Right[0] = -1;
v.pb(0);
for(int i=1; i<N; i++){
Left[i] = Right[i] = -1;
while(!v.empty() && query(v.back(), i, i, i)==1){
Left[i] = v.back();
v.pop_back();
}
if(v.empty()){
r = i;
}else{
Right[v.back()] = i;
}
v.pb(i);
}
while(!v.empty()) v.pop_back();
return r;
}
/*
int le[MAX_N+1], ri[MAX_N+1];
int main(){
int n;
scanf("%d", &n);
cout<<solve(n, le, ri)<<endl;
for(int i=0; i<n; i++){
cout<<le[i]<<" "<<ri[i]<<endl;
}
}*/
