#include<bits/stdc++.h>
#define endl '\n'
#define X first
#define Y second
void speed()
{
std::ios_base::sync_with_stdio(0);
std::cin.tie(0);
std::cout.tie(0);
}
const int maxn = 1e5 + 10, sq = 200;
int n, m, q, x, y;
int dp[maxn];
std::vector<int> v[maxn], v1[maxn];
std::vector<std::pair<int,int>> s[maxn], s1[maxn];
bool used[maxn], banned[maxn], can[maxn];
bool cmp1(const std::pair<int,int>& p1, const std::pair<int,int>& p2)
{
if(p1.Y == p2.Y) return p1.X < p2.X;
return p1.Y < p2.Y;
}
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 small(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;
}
inline void dfs1(const int i)
{
used[i] = 1;
s[i].push_back({0, i});
for(const int& nb : v1[i])
{
if(!used[nb]) dfs1(nb);
for(const std::pair<int,int>& j : s1[nb])
{
s[i].push_back({j.X + 1, j.Y});
}
}
std::sort(s[i].begin(), s[i].end(), cmp1);
for(int j = 0; j < (int)s[i].size(); )
{
int bestDist = s[i][j].X;
const int node = s[i][j].Y;
int k = j + 1;
while(k < (int)s[i].size() && s[i][k].Y == node)
{
bestDist = std::max(bestDist, s[i][k].X);
k++;
}
s1[i].push_back({bestDist, node});
j = k;
}
std::sort(s1[i].rbegin(), s1[i].rend());
while((int)s1[i].size() > sq +1)
{
s1[i].pop_back();
}
}
inline int large(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.Y]) return j.X;
}
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 << small(x, y) << endl;
}
else
{
std::cout << large(x, y) << endl;
}
}
return 0;
}
