int dfn[MAXN],low[MAXN],cnt;

bool isbridge[MAXN];

void tarjan(int x,int edg)

{

    low[x]=dfn[x]=++cnt;

    for(int i=f(x);i;i=n(i))

    if(!dfn[v(i)])

    {

        tarjan(v(i),i);

        low[x]=min(low[x],low[v(i)]);

        if(low[v(i)]>dfn[x])

            isbridge[i]=isbridge[i^]=;

    }

    else if(i!=(edg^))low[x]=min(low[x],dfn[v(i)]);

}

int c[MAXN],dcc;

void dfs(int x,int dcc)

{

    c[x]=dcc;

    for(int i=f(x);i;i=n(i))

    if(!c[v(i)]&&!isbridge[i])

        dfs(v(i),dcc);

}

signed main()

{

    for(int i=;i<=n;i++)

    if(!dfn[i])tarjan(i,);

    for(int i=;i<=n;i++)

    if(!c[i])dcc++,dfs(i,dcc);

    for(int i=;i<=num_e;i++)

    if(c[u(i)]!=c[v(i)])

        du[c[u(i)]]++;

}