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#include<deque>
#include<vector>
#include<cstring>
#include<algorithm>
using namespace std;
struct {
int u,v;
edge(){}
edge(int uu,int vv):u(uu),v(vv){}
};
const int maxn = 20001;
int t,n,m;
vector<int> G[maxn];
int dfn[maxn],low[maxn],sccno[maxn],in[maxn],out[maxn];
int ntime,bcc_cnt;
deque<int> P;
void tarjan(int u){
dfn[u] = low[u] = ++ntime;
P.push_back(u);
for(int i=0;i<G[u].size();i++){
int v = G[u][i];
if(!dfn[v]){
tarjan(v);
low[u] = min(low[u],low[v]);
}
else if(!sccno[v]){
low[u] = min(low[u],dfn[v]);
}
}
if(low[u]==dfn[u]){
bcc_cnt++;
int tmp;
do{
tmp = P.back();
P.pop_back();
sccno[tmp] = bcc_cnt;
}while(tmp!=u);
}
}
void find_bcc(int n){
memset(sccno,0,sizeof(sccno));
memset(dfn,0,sizeof(dfn));
ntime = bcc_cnt = 0;
for(int i=0;i<n;++i)if(!dfn[i])tarjan(i);
}
int main(){
scanf("%d",&t);
while(t--){
for(int i=0;i<n;++i)G[i].clear();
scanf("%d%d",&n,&m);
for(int i=0;i<m;i++){
int a,b;
scanf("%d%d",&a,&b);
a--;
b--;
G[a].push_back(b);
}
find_bcc(n);
for(int i=1;i<=bcc_cnt;i++)in[i] = out[i] = 1;
for(int u=0;u<n;u++)
for(int i=0;i<G[u].size();i++){
int v = G[u][i];
if(sccno[u]!=sccno[v])
in[sccno[v]] = out[sccno[u]] = 0;
}
int a = 0,b=0;
for(int i=1;i<=bcc_cnt;i++){
if(in[i])a++;
if(out[i])b++;
}
int ans = max(a,b);
if(bcc_cnt==1)ans = 0;
printf("%dn",ans);
}
return 0;
}
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