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

struct S {
	int l, r, v;
};
struct T {
	int a, b;
};
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;

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

	set<pair<int,int>> done;

	q.push({a, b, 0});
	int I = 0;
	while(!q.empty() && ++I < 1000000) {
		int l = q.top().l, r = q.top().r, d = q.top().v + 1;
		if(!done.insert({l,r}).second) continue;
		q.pop();
		for(T t : {T{g[l].r, g[r].r}, T{g[l].l, g[r].l}}) {
			int a = t.a, b = t.b;
			if(g[a].v != g[b].v) {
				cout << d << endl;
				return 0;
			}
			q.push({a, b, d});
		}
	}

	cout << "INDISTINGUISHABLE" << endl;
	return 0;
}