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

struct UnionFind {
	vector<int> par, rank, size;
	int c;
	UnionFind(int n) : par(n), rank(n, 0), size(n, 1), c(n) {
		for(int i = 0; i < n; ++i) par[i] = i;
	}
	int find(int i) { return (par[i] == i ? i : (par[i] = find(par[i]))); }
	bool same(int i, int j) { return find(i) == find(j); }
	int get_size(int i) { return size[find(i)]; }
	int count() { return c; }
	void merge(int i, int j) {
		if((i = find(i)) == (j = find(j))) return;
		c--;
		if(rank[i] > rank[j]) swap(i, j);
		par[i] = j;
		size[j] += size[i];
		if(rank[i] == rank[j]) rank[j]++;
	}
};
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;
	UnionFind uf(n);
	queue<S> q;
	q.push({a, b, 0});
	while(!q.empty()) {
		int a = q.front().l, b = q.front().r, d = q.front().v;
		q.pop();
		if(uf.same(a, b)) continue;
		if(g[a].v != g[b].v) {
			cout << d << endl;
			return 0;
		}
		uf.merge(a, b);
		for(T t : {T{g[a].l, g[b].l}, T{g[a].r, g[b].r}}) {
			int a = t.a, b = t.b;
			q.push({a, b, d + 1});
		}
	}

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