#include <iostream>
#include <fstream>
using namespace std;

ifstream f("darb.in");
ofstream g("darb.out");

int n,m,t[100001],v[100001],nr;

struct nod{
    int info;
    nod *next;
} *l[100001];


void drum(int y){
    if(y!=0) v[++nr]=y;
    else return;
    drum(t[y]);
}

int bf(int x){
    int i,p,u;
    int q[100001],viz[100001];
    nod *nod;
    
    for(i=1;i<=n;i++) t[i]=viz[i]=0;
    viz[x]=p=u=1;
    q[p]=x;

    while(p<=u){
        viz[q[p]]=1;
        nod=l[q[p]];
        while(nod!=NULL) {
            if(viz[nod->info]==0){
                q[++u]=nod->info;
                viz[nod->info]=1;
                t[nod->info]=q[p];
            }
            nod=nod->next;
        }
        p++;
    }
    return q[u];
}



int main() {
    int i,x,y,frunza;
    nod *p;
    
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        p=new nod;
        p->info=y;
        p->next=l[x];
        l[x]=p;
        p=new nod;
        p->info=x;
        p->next=l[y];
        l[y]=p;
    }
    
    frunza=bf(1);
    frunza=bf(frunza);
    drum(frunza);
   // cout<<"Centrul este: ";
    //if(nr%2==1) cout<<v[nr/2];
    //else cout<<v[nr/2]<<" "<<v[nr/2+1];
    g<<nr;
    return 0;
}