#include <stdio.h>
#include <vector>
#include <queue>
#define maxi 100001
std::vector<int> legaturi[maxi];
std::queue<int> coada;
int viz[maxi], dist[maxi], nodCurent, vecin, i, ultim, prim;
void BFS(int nodPlecare)
{
    memset(viz, 0, sizeof(int)*maxi);
    memset(dist, 0, sizeof(int)*maxi);
    
    coada.push(nodPlecare);
    
    while(!coada.empty())
    {
        nodCurent = coada.front();
        for(i = 0; i < legaturi[nodCurent].size(); i++)
        {
            vecin = legaturi[nodCurent][i];
            if(viz[vecin] == 0)
            {
                viz[vecin] = 1;
                coada.push(vecin);
                dist[vecin] = dist[nodCurent] + 1;
                
                ultim = vecin;
            }
        }
        coada.pop();
    }
    
}
int main()
{
    FILE *inputFile = fopen("darb.in", "r"), *outputFile = fopen("darb.out", "w");
    
    int i, x, n, y;
    
    fscanf(inputFile, "%d", &n);
    
    for(i = 0; i < n; i++)
    {
        fscanf(inputFile, "%d %d", &x, &y);
        legaturi[x].push_back(y);
        legaturi[y].push_back(x);
        prim = x;
    }
    
    BFS(prim);
    BFS(ultim);
    
    fprintf(outputFile, "%d", dist[ultim] + 1);
    
    return 0;
}