#include <map>
#include <set>
#include <vector>
#include <fstream>
#include <iostream>
#include <stack>

using namespace std;

map<int, vector<int> > graph;
stack<int> st;
set<int> used;

bool dfs(int S, int T) {
    used.insert(S);
    st.push(S);
    while (!st.empty()) {
        int v = st.top(); st.pop();
        if (v == T) return true;
        vector<int> & to = graph[v];
        for (int i = 0; i < to.size(); ++i) if (!used.count(to[i])) {
            used.insert(to[i]);
            st.push(to[i]);
        }
    }
    return false;
}

int main() {
    setlocale(LC_ALL, ".1251");
    ifstream fin("input.txt");
    int s, t, m;
    fin >> m >> s >> t;
    while (m--) {
        int x, y;
        fin >> x >> y;
        graph[x].push_back(y);
    }
    cout << (dfs(s, t) ? "Да\n" : "Нет\n");
    return 0;
}