#include <bits/stdc++.h> using namespace std; #define int long long #define ld long double #define pii pair<int, int> #define fi first #define se second #define __builtin_popcount __builtin_popcountll #define all(x) (x).begin(), (x).end() #define debug(a, l, r) for (int i = (l); i <= (r); ++i) cout << (a)[i] << ' '; cout << '\n'; const int MAXN = 1e5 + 5; const int INF = 1e18 + 7; int n, m, q; vector<int> radj[MAXN]; void init() { cin >> n >> m >> q; for (int i = 1; i <= m; ++i) { int u, v; cin >> u >> v; radj[v].push_back(u); } } namespace subtask12{ int dp[MAXN]; bitset<MAXN> mark; bool check() { return (q == 1); } void solve() { int t, y; cin >> t >> y; mark.set(); for (int i = 1; i <= y; ++i) { int c; cin >> c; mark[c] = 0; } for (int i = 1; i <= n; ++i) dp[i] = -INF; dp[t] = 0; for (int i = n; i >= 1; --i) { if (dp[i] == -INF) continue; for (int j : radj[i]) { dp[j] = max(dp[j], dp[i] + 1); } } int res = -INF; for (int i = 1; i <= n; ++i) if (mark[i]) res = max(res, dp[i]); cout << (res == -INF ? -1 : res); } } signed main() { #ifdef NCTHANH freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); #endif ios_base::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr); init(); if (subtask12::check()) return subtask12::solve(), 0; return 0; }