#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#define maxN 100001
#define M -2000000000
using namespace std;
FILE *f=fopen("darb.in","r");
FILE *g=fopen("darb.out","w");
queue<int>q;
vector<int>L[maxN];
bool viz[maxN];
int n,maxx,max1=M,max2=M,niv[maxN];
void bfs(int i)
{
    memset(viz,false,sizeof(viz));
    memset(niv,0,sizeof(niv));
    viz[1]=1;
    int xcur,j;
    q.push(i);
    viz[i]=true;
    niv[i]=1;
    while(!q.empty())
    {
        xcur=q.front();
        q.pop();
        for(j=0;j<L[xcur].size();j++)
            if(viz[L[xcur][j]]==false)
            {
            viz[L[xcur][j]]=true;
            niv[L[xcur][j]]=niv[xcur]+1;
            maxx=niv[L[xcur][j]];
            q.push(L[xcur][j]);
            }
    }
}
int main()
{
    int i,x,y,j;
    fscanf(f,"%d",&n);
    for(i=1;i<n;i++)
    {
        fscanf(f,"%d%d",&x,&y);
        L[x].push_back(y);
        L[y].push_back(x);
    }
    viz[1]=1;
    for(j=0;j<L[1].size();j++)
    {
        bfs(L[1][j]);
        if(maxx>=max1)
        {
            max2=max1;
            max1=maxx;
        }
        else if(maxx>max2)max2=maxx;
    }
    if(max1==M)max1=-1;
    fprintf(g,"%d",max1+max2+1);
    return 0;
}