#include <bits/stdc++.h>
using namespace std;

struct S {
	int l, r, v;
};
struct T {
	int a, b;
};
struct pair_hash {
	std::size_t operator()(const std::pair<int,int>& p) const { 
		return std::hash<int>()(p.first) ^ (std::hash<int>()(p.second) << 3);
	}
};
int main() {
	int n, a, b;
	cin >> n >> a >> b;
	vector<S> g(n);
	for(auto &x : g) cin >> x.l >> x.r >> x.v;

	if(g[a].v != g[b].v) {
		cout << 0 << endl;
		return 0;
	}

	constexpr int MI = 5e7;

	unordered_map<pair<int,int>, int, pair_hash> done;
	done.reserve(MI);

	vector<S> q;
	q.reserve(MI);
	q.push_back({a, b, 0});
	done[{a,b}] = 0;
	int I = 0;
	int m = 2e9;


	auto start = chrono::high_resolution_clock::now();

	while(!q.empty()) {
		if((I&((1<<10)-1))==0){
			auto now = chrono::high_resolution_clock::now();
			if(chrono::duration<double,ratio<1>>(now-start).count() > 1.3)
				break;
		}
		int l = q.back().l, r = q.back().r, d = q.back().v + 1;
		q.pop_back();
		//cerr << l << ' ' << r << ' ' << d << endl;

		if(done[{l,r}] != d-1){
			//cerr << "Not optimal; continue\n";
			continue;
		}

		T tl{g[l].l, g[r].l}, tr{g[l].r, g[r].r};
		if(rand() & (1<<5)) swap(tl, tr);
		for(T t : {tl, tr}) {
			int a = t.a, b = t.b;
			if(g[a].v != g[b].v) {
				//cerr << "New min: " << g[a].v << " " << g[b].v << endl;
				m = min(m, d);
				break;
			}
			if(d>=m) continue;
			//cerr << "ab: " << a << ' ' << b << endl;
			auto it = done.find({a,b});
			bool push = true;
			if(it == done.end())
				done[{a,b}] = d;
			else if(d < it->second)
				done[{a,b}] = d;
			else {
				push = false;
				//cerr << "nopush\n";
			}
			if(push){
				q.push_back({a, b, d});
				//cerr << "push: " << a << ' ' << b << ' ' << d << endl;
			}
		}
	}
	if(m < 2e9)
		cout << m << endl;
	else
		cout << "INDISTINGUISHABLE" << endl;
	return 0;
}