#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;

	int I = 0;
	int m = n+10;

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

	while(true) {
		if((++I&((1<<10)-1))==0){
			auto now = chrono::high_resolution_clock::now();
			if(chrono::duration<double,ratio<1>>(now-start).count() > 1.0)
				break;
		}
		int u=a, v=b, d=0;
		while(g[u].v == g[v].v && ++d < m){
			if(rand() & (1<<5))
				u = g[u].l, v = g[v].l;
			else
				u = g[u].r, v = g[v].r;
		}
		m = d;
	}
	if(m <= n)
		cout << m << endl;
	else
		cout << "INDISTINGUISHABLE" << endl;
	return 0;
}