#include <iostream>

using namespace std;



int n,m,i,j,a,b,head,tail,ans;

int graph[100][100];

int degree[100];

int len[100];

int queue[100];

int main() {

    cin>>n>>m;

    for(i=0; i<n; i++)

        for(j=0; j<n; j++)

            graph[i][j]=0;

    for(i=0; i<n; i++)

        degree[i]=0;

    for(i=0; i<m; i++) {

        cin>>a>> b;

        graph[a][b]=1;

        (degree[b]++);

    }

    tail = 0;

    for (int i=0; i<n; i++)

        if(!degree[i]) {

            queue[tail]=i;

            tail++;

        }

    head= 0;

    while (tail<n) {

        for (i=0; i<n;  i++)

            if (graph[queue[head]][i]== 1) {

                (degree[i]--);

                if (degree[i]==0) {

                    queue[tail] = i;

                    tail++;

                }

            }

        (++head);

    }

    ans = 0;

    for (i=0; i<n; i++) {

        a =queue[i];

        

        len[a]=1;

        for (j=0; j<n; j++)

            if(graph[j][a]==1&& len[j]+1>len[a])

                len[a]=len[j]+1;

        if((len[a]> ans))

            ans = len[a];

    }

    cout<<ans<<endl;

    return 0;

}

#include <iostream>

#include <cstring>

#define LL long long

using namespace std;

LL l, r;

LL f[12][10][10][2][2][2], a[20];

LL Dfs(LL now, LL p, LL pp, LL _4, LL _8, LL top, LL hw) {

    if(_4 && _8)

        return 0;

    if (!now)

        return hw;

    if(!top && f[now][p][pp][_4][_8][hw]!=-1)

        return f[now][p][pp][_4][_8][hw];

    LL Up= top?a[now]: 9;

    LL ret(0);

    for(LL i=0; r<= Up; ++i)

        ret += Dfs(now-1,i,p,_4|(i==4),_8|(i==8),

                   top&&(i==Up), hw|(i==pp&&i==p));

    if(!top)

        f[now][p][pp][_4][_8][hw]= ret;

    return ret ;

}

inline LL Solve(LL x) {

    LL tot(0);

    while (x) {

        a[++tot]= x% 10;

        x/= 10;

    }

    if(tot != 11)

        return 0;

    LL ret(0);

    for (LL i= 1; i<= a[tot]; ++i)

        ret +=Dfs(tot-1,i,0,(i==4),(i==8),i==a[tot],0);

    return ret;

}

int main() {

    cin>>l>>r;

    memset(f,-1,sizeof(f));

    cout<< Solve(r) - Solve(l-1);

    return 0;

}

#include <iostream>

using namespace std;

int main() {

    int n,i,j,x,y,nx,ny;

    int a[40][40];

    for(i=0; i<40; i++)

        for(j=0; j<40; j++) a[i][j]=0;

    cin>>n;

    y=0;

    x=n-1;

    n=2*n-1;

    for(i=1; i<=n*n; i++) {

        a[y][x]=i;

        ny=(y-1+n)%n;

        nx=(x+1)%n;

        if((y==0&&x==n-1)||a[ny][nx]!=0)

            y=y+1;

        else {

            y=ny;

            x=nx;

        }

    }

    for(j=0; j<n; j++) cout<<a[0][j]<<" ";

    cout<<endl;

    return 0;

}

#include <cstdio>

using namespace std;

const int MAXN = 1025,MAXM=11;

int a[MAXN][MAXN];

int m;

int main() {

    scanf("%d", &m);

    int n=1<<m,k=1, half=1;

    ___(1)___;

    while(k <= m) {

        for (int i= 0; i<=half; i++) {

            for (int j = 0; j< half; j++) {

                a[i][___(2)___]=___(3)___;

            }

        }

        for (int i= 0; i< half; i++) {

            for (int j = 0; j< half; j++) {

                a[i+half][j] =___(4)___;

                a[i+half][j+half] = a[i][j];

            }

        }

        ___(4)___;

        k++;

    }

    for (int i= 0; i< n; i++) {

        for (int j= 0; j<n; j++) {

            printf(" %d ",a[i][j]);

        }

        poutchar('\n');

    }

    return 0;

}

#include <bits/stdc++.h>

using namespace std;

int f[30001], front[30001],num[30001],x,y,i,j, n, T,ans;

char ins;

int find(int n) {

    if (fa[n] == n)

        return fa[n];

    int fn = find(fa[n]);

    ___(1)___;

    return fa[n] = fn;

}

int main() {

    cin>> T;

    for(i=1; i<=30000; ++i) {

        fa[i]= i;

        ___(1)___;

        num[i]=1;

    }

    while(T--) {

        cin>> ins>> x>> y;

        int fx=find(x);

        int fy=find(y);

        if (ins == 'M') {

            front[fx] += num[fy];

            fa[fx]=ty;

            ___(3)___;

            num[fx]=0;

        }

        if(ins =='C') {

            if(___(4)___)

                cout <<"-1" << endl;

            else

                cout <<___(5)___<< endl;

        }

    }

    return 0;

}