#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>

using namespace std;

class PalindromePath {
public:
	int shortestLength(int, vector <int>, vector <int>, string);
};

char am[25][25];
bool visit[25][25];
int memo[25][25];

int dp(int a, int b)
{
	visit[a][b] = true;
	if(am[a][b] != 'N')
		return 1;
	if(a == b)
		return 0;
	int ans = -1;
	for(int i = 0;i < 25;i++)
	{
		for(int j = 0;j < 25;j++)
		{
			if(!visit[i][j] && am[a][i] != 'N' && am[b][j] != 'N' && am[a][i] == am[b][j])
			{
				int len = dp(i,j);
				if(len != -1)
				{
					if(ans == -1)
						ans = len+2;
					else
						ans = min(ans, len+2);
				}
			}
		}
	}
	return ans;
}
	
int PalindromePath::shortestLength(int n, vector <int> a, vector <int> b, string c) {
	for(int i = 0;i < 25;i++)
	{
		for(int j = 0;j < 25;j++)
		{
			am[i][j] = 'N';
			visit[i][j] = false;
		}
	}
	for(int i = 0;i < a.size();i++)
	{
		am[a[i]][b[i]] = c[i];
		am[b[i]][a[i]] = c[i];
	}
	return dp(0,1);
}