#include <iostream>
#include <map>
#include <set>
#include <string>
using namespace std;

#ifdef DBG
#define PDBG(X) { cout<<X<<endl; }
#else 
#define PDBG(X) 
#endif

typedef map<int, set<int> > Adj;

Adj Graph;
map<string, int> NodeIndex;
set<int> Visited;

int NodeLen,
	root,
	steps,
	maxVal;

void findMax (int parent, int child)
{
	set<int>::iterator iter;

	PDBG("Parent :"<<parent<<" child :"<<child);
	if(Visited.find(child) != Visited.end() ) {
		PDBG(child<<" repeats");
		return;
	}

	if(Graph[child].find(child) != Graph[child].end())
		return;

	//Check if No visited,  except parent loves child
	for(iter = Visited.begin(); iter != Visited.end(); iter++ ) {
		if(*iter != parent && Graph[*iter].find(child)!= Graph[*iter].end()) {
			PDBG("Child "<<child<<" loves "<<*iter);
			return;
		}
	}

	// check that the child does not love anybody in the Visited set 
	// If it loves the root, then finish the loop
    for (iter = Graph[child].begin(); iter != Graph[child].end(); iter++) {
		if (*iter != root && Visited.find(*iter) != Visited.end()) {
			PDBG("Child "<<child<<" loves Visited at "<<*iter<<" with root "<<root);
			return;
		}
	}
	if (Graph[child].find(root) != Graph[child].end()) {
            // Only connects to root, Finalize
		if (maxVal < steps+1) {
			maxVal = steps+1;
			PDBG("\t Value Set :"<<maxVal)
		}
		return;
	}
    
	Visited.insert(child);
	for (set<int>::iterator iter= Graph[child].begin(); iter!= Graph[child].end(); iter++) {
		steps++;
		findMax(child, *iter);
		steps--;
	}
	Visited.erase(child);
}

int main()
{
	int n;
	cin>>n;

	NodeLen = 1;
	for (int i=0; i<n; i++) {
		string lhs, rhs;
		int li, ri;
		cin>>lhs>>rhs;

		if ( (li = NodeIndex[lhs]) == 0)
			li = (NodeIndex[lhs] = NodeLen++);
		if ( (ri = NodeIndex[rhs]) == 0)
			ri = (NodeIndex[rhs] = NodeLen++);

		Graph[li].insert(ri);
	}

	maxVal = 0;
	for (root = 1; root < NodeLen; root++) {
		steps = 1;
		if(Graph[root].find(root) != Graph[root].end())
			continue;
		Visited.insert (root);
		PDBG("Root :"<<root);
		for (set<int>::iterator iter = Graph[root].begin(); iter != Graph[root].end(); iter++)
		{
			findMax(root, *iter);
		}
		Visited.erase(root);
	}
	if(maxVal>2)
        cout<<maxVal<<endl;
	else 
		cout<<0<<endl;

	return 0;
}