programming.in.th - 1031

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

const int N = 10010;

vector<int> G[N];
bool vis[N];
int dist[N];

int main()
{
    int k, n, m;
    scanf("%d%d%d", &k, &n, &m);
    for (int i = 0; i < m; ++i) {
        int u, v;
        scanf("%d%d", &u, &v);
        G[u].push_back(v);
    }
    queue<int> Q;
    dist[1] = 0;
    vis[1] = true;
    Q.push(1);
    int mx = 1;
    while (!Q.empty()) {
        int u = Q.front();
        Q.pop();
        if (dist[u] > k)
            continue;
        mx = max(mx, u);
        for (auto v : G[u]) {
            if (!vis[v]) { // you can also check (dist[u]+1 <= k) if you want faster time
                dist[v] = dist[u]+1; // can also do mx = max(mx, v); here for faster time
                vis[v] = true;
                Q.push(v);
            }
        }
    }
    printf("%d\n", mx);

    return 0;
}