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#include <stdio.h>#include <stdlib.h>#include <vector>using namespace std;#define MAX_V    2001#define FOR(t,i,n) for(t i=0;i<n;i++)#define FIT(t,i,c) for(t::iterator i=c.begin();i!=c.end();i++)typedef vector<long> _vector_long;_vector_long adj[MAX_V];            //Adjacency vector representation of graph_vector_long adj_t[MAX_V];            //Adjacency vector representation of transpose of graphlong order[MAX_V], finish[MAX_V], scc_number[MAX_V];long t_time, scc_num;char color[MAX_V];char scc_in[MAX_V];            //1 if there are outgoing vertices from this SCClong V, E;int compare(const void *a, const void *b){    long aa = *(long *)a;    long bb = *(long *)b;    return finish[bb]-finish[aa];}void DFS_visit(_vector_long adj[], long u){    scc_number[u]=scc_num;    color[u]=0;    t_time++;    FIT(_vector_long,i,adj[u]) {        if(color[*i]==1) {            DFS_visit(adj, *i);        }    }    finish[u]=t_time=t_time+1;}long DFS(_vector_long adj[]){    long count=0;            //Keeps a count of the number of DFS forests    scc_num=0;    t_time=0;    FOR(long,i,V)         color[i]=1;        //1 --> NOT VISITED, 0 --> VISITED    FOR(long,i,V) {        if(color[order[i]]==1) {            count++;             DFS_visit(adj, order[i]);            scc_num++;        }    }    return count;}int main(){    scanf("%ld %ld", &V, &E);    FOR(long,i,E) {        long f, t;        scanf("%ld %ld", &f, &t);        adj[f-1].push_back(t-1);        adj_t[t-1].push_back(f-1);    }    //Compute the number of strongly connected components    FOR(long, i, V) order[i]=i;    //Initial order for DFS, numerical    //Compute the finish times    DFS(adj);    //Reorder order according to finish    qsort(order, V, sizeof(long), compare);    long count=DFS(adj_t);    //memset(scc_in, 0, sizeof(scc_in));    --- scc_in made global    FOR(long,i,V)         FIT(_vector_long,j,adj[i]) {            if(scc_number[i]!=scc_number[*j]) {                scc_in[scc_number[*j]]=1;            }        }    long ans=0;    FOR(long,i,count) ans+=scc_in[i];    count-=ans;    printf("%ld\n", count);    return 0;}