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

struct S {
	int l, r, v;
};

int n;
vector<S> g;

int bfs(int a, int b){
	queue<S> q;
	vector<bool> done(n, false);
	q.push({a, b, 0});
	while(!q.empty()) {
		int l = q.front().l, r = q.front().r, d = q.front().v;
		//cerr << "visit: " << l << ' ' << r << ' ' << d << endl;
		q.pop();
		if(g[l].v != g[r].v){
			//cerr << "RETURN " << d << endl;
			return d;
		}
		if(done[l]) continue;
		done[l] = true;
		q.push({g[l].l, g[r].l, d+1});
		q.push({g[l].r, g[r].r, d+1});
	}
	return n+10;
}

int main() {
	int a, b;
	cin >> n >> a >> b;
	g.resize(n);
	for(auto &x : g) cin >> x.l >> x.r >> x.v;

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

	int d = min(bfs(a,b), bfs(b,a));
	if(d <= n)
		cout << d << endl;
	else
		cout << "INDISTINGUISHABLE" << endl;
	return 0;
}