#include <iostream>
#include <cstring>
#include <string>
#include <algorithm>
#include <map>
#include <vector>
#include <set>
#include <queue>
#include <cstdlib>
#include <cstdio>
using namespace std;
const int maxn = 507;

vector<string> S;
map<string, int> idx;

vector<int> g[maxn];
bool used[maxn];
int d[maxn];
int bfs(int st)
{
    memset(used, 0, sizeof(used));
    memset(d, 0, sizeof(d));
    queue<int> Q;
    Q.push(st);
    d[st] = 0;
    used[st] = true;
    while (!Q.empty())
    {
        int v = Q.front();
        Q.pop();

        for (int i = 0; i < g[v].size(); ++i)
        {
            int to = g[v][i];
            if (!used[to])
            {
                Q.push(to);
                d[to] = d[v] + 1;
                used[to] = true;
            }
            else
            {
                return d[v] + d[to] + 1;
            }
        }
    }
    return 0;
}

int main()
{
    //freopen("input.txt", "r", stdin);
    int n;
    cin >> n;
    vector<pair<string, string> > Q;
    for (int i = 0; i < n; ++i)
    {
        string a, b;
        cin >> a >> b;
        Q.push_back(make_pair(a, b));
        S.push_back(a);
        S.push_back(b);
    }
    sort(S.begin(), S.end());
    S.resize(distance(S.begin(), unique(S.begin(), S.end())));

    for (int i = 0; i < (int)S.size(); ++i)
    {
        idx[S[i]] = i;
    }

    for (int i = 0; i < n; ++i)
    {
        int a = idx[Q[i].first],
            b = idx[Q[i].second];
        g[a].push_back(b);
    }

    int ans = 0;
    for (int i = 0; i < (int)S.size(); ++i)
    {
        ans = max(ans, bfs(i));
    }
    if (ans < 3)
    {
        cout << 0;
    }
    else
    {
        cout << ans;
    }

    return 0;
}