#include<bits/stdc++.h>
typedef long long   ll;
#define endl        '\n'
#define F           first
#define S           second
#define pb          push_back
#define yes         cout<<"YES\n"
#define no          cout<<"NO\n"
#define all(x)      x.begin(),x.end()
#define allr(x)     x.rbegin(),x.rend()
#define error1(x)   cerr<<#x<<" = "<<(x)<<endl
#define error2(a,b) cerr<<"("<<#a<<", "<<#b<<") = ("<<(a)<<", "<<(b)<<")\n";
#define coutall(v)  for(auto &it: v) cout<<it<<" "; cout<<endl;
#define _ASRafi__   ios::sync_with_stdio(false); cin.tie(0);
using namespace std;

const int N = 1e3 + 7;
vector<int> g[N];
string s1;
int ans = 0;

bool isPalindrome(string &s)
{
    for (int i = 0; i < int(s.size()) >> 1; i++)
    {
        if (s[i] != s[int(s.size()) - i - 1])
        {
            return 0;
        }
    }
    return 1;
}

void dfs(int vertex, int par, string &s)
{
    if(g[vertex].size() == 0)
    {
        // cout << s << endl;
        if(ans < s.size() && isPalindrome(s)) ans = max(ans, int(s.size()));
        return;
    }
    for(auto &child: g[vertex])
    {
        if(child == par) continue;
        s.pb(s1[child]);
        dfs(child, vertex, s);
        s.pop_back();
    }
    return;
}

void solve()
{
    int n, q;
    cin >> n >> s1;
    for (int i = 0; i + 1 < n; i++)
    {
        int u, v; cin >> u >> v;
        g[u].pb(v);
    }
    s1 = '#' + s1;
    cin >> q;
    string s;
    while(q--)
    {
        int i; char ch;
        cin >> i >> ch;
        if(s1[i] != ch)
        {
            // cout << i << " ---- " << ch << endl;
            ans = 0;
            s1[i] = ch;
            s += s1[1];
            dfs(1, 0, s);
            s.pop_back();
        }
        cout << ans << endl;
    }
    return;
}

int32_t main()
{
    _ASRafi__;
    int tc = 1;
    // cin >> tc;
    for (int t = 1; t <= tc; t++)
    {
        // cout << "Case " << t << ": ";
        solve();
    }
    return 0;
}