G - Security Badge

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fastio ios::sync_with_stdio(false), cin.tie(0);
#define pb push_back
#define all(x) x.begin(), x.end()

const ll MAXN = 1e3 + 5;
struct node
{
    ll next, c, d;
};

ll N, M, K;
vector<node> G[MAXN];
vector<ll> tmp;
ll s, t, vis[MAXN];

void dfs(ll now, ll pass)
{
    vis[now] = 1;
    for (auto it : G[now])
    {
        if (!vis[it.next] && it.c <= pass && pass <= it.d)
        {
            vis[it.next] = 1;
            dfs(it.next, pass);
        }
    }
}

bool iniDfs(ll pass)
{
    for (ll i = 0; i < N; i++)
        vis[i] = 0;
    dfs(s, pass);
    return vis[t];
}

void init()
{
    cin >> N >> M >> K;
    cin >> s >> t;
    s--;
    t--;
    ll x, y, a, b;
    for (ll i = 0; i < M; i++)
    {
        cin >> a >> b >> x >> y;
        a--;
        b--;
        tmp.pb(x);
        tmp.pb(y);
        G[a].pb({b, x, y});
    }
    sort(all(tmp));
    tmp.resize(unique(all(tmp)) - tmp.begin());
}

void solve()
{
    ll ans = 0;
    ll last = tmp[0];
    for (ll i = 1; i < tmp.size(); i++)
    {
        if (iniDfs(last))
        {
            ans += tmp[i] - last + 1;
        }
        last = tmp[i] + 1;
    }
    cout << ans << "\n";
}

signed main()
{
    fastio
    init();
    solve();
    return 0;
}