#include<iostream>
#include<vector>
#include<algorithm>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx")
#pragma GCC target("avx2")
#pragma GCC target("fma")
#pragma GCC target("sse")
#pragma GCC target("sse2")
#pragma GCC target("sse3")
#pragma GCC target("ssse3")
#pragma GCC target("sse4")
#pragma GCC target("popcnt")
inline void speed()
{
std::ios_base::sync_with_stdio(0);
std::cin.tie(0);
std::cout.tie(0);
}
const int maxn = 1e5 + 10, sq =90;
int n, m, q, x, y;
int dp[maxn],mx[maxn];
std::vector<int> v[maxn], v1[maxn];
std::vector<std::pair<int,int>> s1[maxn];
bool used[maxn], banned[maxn], can[maxn];
inline void read()
{
std::cin >> n >> m >> q;
int x1, y1;
for(int i = 1; i <= m; i++)
{
std::cin >> x1 >> y1;
v[x1].push_back(y1);
v1[y1].push_back(x1);
}
}
inline void dfs(const int i)
{
used[i] = 1;
for(const int& nb : v[i])
{
if(!used[nb]) dfs(nb);
if(can[nb])
{
dp[i] = std::max(dp[i], dp[nb] + 1);
can[i] = 1;
}
}
}
inline int large(const int x, const int y)
{
for(int i=1; i<=n; i++)
{
used[i]=banned[i]=dp[i]=can[i]=0;
}
can[x]=1;
for(int i=x; i>=1; i--)
{
if(used[i]==0)
{
dfs(i);
}
}
int node;
for(int i=1; i<=y; i++)
{
std::cin>>node;
banned[node]=1;
}
int ans=-1;
for(int i=1; i<=x; i++)
{
if(banned[i]==1||can[i]==0)
{
continue;
}
ans=std::max(ans,dp[i]);
}
if(ans==0&&banned[x]==1)
{
return -1;
}
return ans;
}
void dfs1(int i)
{
std::vector<int> nodes = {i};
mx[i] = 0;
used[i]=1;
for(const int& nb : v1[i])
{
if(used[nb]==0)
dfs1(nb);
for(const auto& j : s1[nb])
{
nodes.push_back(j.second);
mx[j.second] = std::max(mx[j.second], j.first + 1);
}
}
sort(nodes.begin(), nodes.end());
s1[i].push_back({mx[nodes[0]], nodes[0]});
mx[nodes[0]] = -1;
for(int j = 1; j < (int)nodes.size(); j++)
{
if(nodes[j] != nodes[j - 1])
{
s1[i].push_back({mx[nodes[j]], nodes[j]});
mx[nodes[j]] = -1;
}
}
sort(s1[i].rbegin(), s1[i].rend());
while((int)s1[i].size() > sq+2)
s1[i].pop_back();
}
inline int small(const int x, const int y)
{
for(int i = 1; i <= n; i++)
{
banned[i] = 0;
}
int node;
for(int i = 1; i <= y; i++)
{
std::cin >> node;
banned[node] = 1;
}
for(const std::pair<int,int>& j : s1[x])
{
if(!banned[j.second]) return j.first;
}
return -1;
}
int main()
{
speed();
read();
for(int i = 1; i <= n; i++)
{
if(!used[i]) dfs1(i);
}
for(int i = 1; i <= q; i++)
{
std::cin >> x >> y;
if(y > sq)
{
std::cout << large(x, y) << '\n';
}
else
{
std::cout << small(x, y) << '\n';
}
}
return 0;
}
