#include <cstdio>
#include <deque>
#include <set>
#include <string>
#include <map>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
using namespace std;
typedef long long LL;
template<class T> inline T& RD(T &x){  
    char c; for (c = getchar(); c < '0'; c = getchar()); x = c - '0'; for (c = getchar(); '0' <= c && c <= '9'; c = getchar()) x = x * 10 + c - '0';  
    return x;  
}
const int inf = 0x3f3f3f3f;
const int maxn = 100005;
int ra[maxn];
int d[maxn];
int fa[maxn];
vector<int> v[maxn];
int dfs(int u){    
    ra[u] = 0;
    for(int i=0;i<v[u].size();i++){
        ra[u]= max(dfs(v[u][i])+1,ra[u]);
    }
    return ra[u];
}
int main(){
    int T;
    scanf("%d",&T);
    while(T --){
        int n,e,m;
        scanf("%d%d%d",&n,&e,&m);
        memset(ra,0,sizeof(ra));    
        memset(d,0,sizeof(d));
        memset(fa,0,sizeof(fa));
        for(int i=1;i<=n;i++)v[i].clear();
        for(int i=0;i<e;i++){
            int a,b;
            scanf("%d%d",&a,&b);
            v[b].push_back(a);
            fa[a] = 1;
        }
        for(int i=1;i<=n;i++){
            if(fa[i] == 0)dfs(i);
        }
        int _max = 0;
        for(int i=1;i<=n;i++){
            d[ra[i]] ++;
            _max = max(_max,ra[i]);
        }
        int cnt = 0,lft = 0;
        for(int i=0;i<=_max;i++){
            int td = d[i];
            if(cnt > i){
                d[i] -= lft;
                if(d[i] < 0){
                    lft -= td;
                    continue;
                }                
            }
            cnt += d[i]/m;
            if(d[i]%m)cnt ++;
            lft = m - d[i]%m;
            if(lft == m)lft = 0;
        }
        printf("%d\n", cnt);
    }
    return 0;
}