#include <bits/stdc++.h>
#define mod 998244353
#define int long long
using namespace std;
int A[10005],B[10005],C[10005],D[10005],f[10005],g[10005],n,cnt;
pair<int,int> dfs(int x)
{
	if(g[x]) return {f[x],g[x]};
	int rtn=1;
	int nw=D[x];
	while(1)
	{
		if(++cnt>=3e7)
		{
			cout << -1;
			exit(0);
		}
		if(A[nw]==C[x])
		{
			nw=B[nw],++rtn;
			break;
		}
		else
		{
			pair<int,int> nx=dfs(nw);
			rtn+=nx.first,nw=nx.second;
		}
	}
	return {f[x]=rtn,g[x]=nw};
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	for(int i=1;i<=n;i++)
	{
		string s;
		cin >> s;
		if(s!="HALT;")
			cin >> A[i] >> s >> B[i] >> s;
		cin >> s >> C[i] >> s >> D[i];
	}
	D[0]=1;
	cout << dfs(0).first-1;
	return 0;
}