#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double dou;
#define pii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define MASK(x) (1LL<<(x))
#define BITj(x, j) (((x)>>(j))&1)
template<typename T> bool maximize(T &x, const T &y) {
if (x < y) {x = y; return 1;}
return 0;
}
template<typename T> bool minimize(T &x, const T &y) {
if (x > y) {x = y; return 1;}
return 0;
}
const int maxn = 1e5+5, B = 400;
int n, m, q;
vector<int> adj[maxn], revadj[maxn];
pii val[maxn][B+5];
int dp[maxn];
bool can[maxn];
namespace sub1{
void solve1(int s, vector<int> &nodes) {
memset(dp, -1, sizeof(dp));
dp[s] = 0;
for (int u : nodes){
can[u] = 0;
}
for (int u = s; u > 1; u--) {
if (dp[u] == -1) continue;
for (int v : revadj[u]) {
maximize(dp[v], dp[u]+1);
}
}
int res = -1;
for (int i = s; i; i--) {
if (can[i]) maximize(res, dp[i]);
}
cout << res << "\n";
for (int u : nodes) {
can[u] = 1;
}
}
void solve() {
for (int i = 0; i <= n; i++) {
can[i] = 1;
}
while (q--) {
int start, sz;
cin >> start >> sz;
vector<int> nodes;
for (int i = 1; i <= sz; i++) {
int u;
cin >> u;
nodes.pb(u);
}
solve1(start, nodes);
}
}
}
namespace sub3{
void prep() {
const pii nostate = {-1, 0};
for (int i = 0; i <= n; i++) {
can[i] = 1;
}
for (int i = 1; i <= n; i++) {
for (int j = 0; j <= B; j++) {
val[i][j] = nostate;
}
}
for (int u = 1; u <= n; u++) {
//init
for (int i = 0; i <= B; i++) {
if (val[u][i].fi < 0) {
val[u][i] = {0, u};
break;
}
}
for (int v : adj[u]) {
pii cur[B+5];
for (int i = 0; i <= B; i++) {
cur[i] = val[v][i];
val[v][i] = nostate;
}
int i = 0, j = 0, pos = 0;
while (pos <= B) {
if ((i > B || val[u][i] == nostate) && (j > B || cur[j] == nostate)) break;
if (i > B || val[u][i] == nostate) {
val[v][pos++] = cur[j++];
continue;
}
if (j > B || cur[j] == nostate) {
val[v][pos++] = make_pair(val[u][i].fi+1, val[u][i].se);
++i;
continue;
}
pii temp = val[u][i];
++temp.fi;
if (temp == cur[j]) {
++j;
continue;
}
if (temp > cur[j]) {
val[v][pos] = temp;
++i;
}
else {
val[v][pos] = cur[j];
++j;
}
++pos;
}
}
}
// for (int i = 1; i <= n; i++) {
// cout << "node " << i << ": ";
// for (int j = 0; j <= min(5, B); j++) {
// cout << "(" << val[i][j].fi << ", " << val[i][j].se << ") ";
// }
// cout << "\n";
// }
}
void solve1(int s, vector<int> &nodes) {
memset(dp, -1, sizeof(dp));
dp[s] = 0;
for (int u : nodes){
can[u] = 0;
}
for (int u = s; u > 1; u--) {
if (dp[u] == -1) continue;
for (int v : revadj[u]) {
maximize(dp[v], dp[u]+1);
}
}
int res = -1;
for (int i = s; i; i--) {
if (can[i]) maximize(res, dp[i]);
}
cout << res << "\n";
for (int u : nodes) {
can[u] = 1;
}
}
void solve2(int s, vector<int> &nodes) {
for (int u : nodes){
can[u] = 0;
}
int j = 0;
while (!can[val[s][j].se]) {
++j;
}
cout << val[s][j].fi << "\n";
for (int u : nodes) {
can[u] = 1;
}
}
void solve() {
//prep val DAG -> case <= B
prep();
while (q--) {
int start, sz;
cin >> start >> sz;
vector<int> nodes;
for (int i = 1; i <= sz; i++) {
int u;
cin >> u;
nodes.pb(u);
}
if (sz >= B) solve1(start, nodes);
else solve2(start, nodes);
}
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
// #define name "task"
// if (fopen(name".inp", "r")) {
// freopen(name".inp", "r", stdin);
// freopen(name".out", "w", stdout);
// }
cin >> n >> m >> q;
for (int i = 1; i <= m; i++) {
int u, v;
cin >> u >> v;
adj[u].pb(v);
revadj[v].pb(u);
}
return sub1::solve(), 0;
}
/*
5 6 3
1 2
2 4
3 4
1 3
3 5
4 5
4 1 1
5 2 2 3
2 3 1 4 5
12 17 10
1 2
2 3
3 4
1 5
2 6
3 7
4 8
5 6
6 7
7 8
5 9
6 10
7 11
8 12
9 10
10 11
11 12
6 3 1 7 12
3 7 1 2 3 4 5 6 7
11 3 1 3 5
9 2 1 9
8 4 1 2 3 4
1 1 1
12 0
10 3 1 6 10
11 8 2 3 5 6 7 9 10 11
8 7 2 3 4 5 6 7 8
*/
