/*
    author:  Maksim1744
    created: 02.07.2023 18:26:57
*/

#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

#define mp   make_pair
#define pb   push_back
#define eb   emplace_back

#define sum(a)     ( accumulate ((a).begin(), (a).end(), 0ll))
#define mine(a)    (*min_element((a).begin(), (a).end()))
#define maxe(a)    (*max_element((a).begin(), (a).end()))
#define mini(a)    ( min_element((a).begin(), (a).end()) - (a).begin())
#define maxi(a)    ( max_element((a).begin(), (a).end()) - (a).begin())
#define lowb(a, x) ( lower_bound((a).begin(), (a).end(), (x)) - (a).begin())
#define uppb(a, x) ( upper_bound((a).begin(), (a).end(), (x)) - (a).begin())

template<typename T>             vector<T>& operator--            (vector<T> &v){for (auto& i : v) --i;            return  v;}
template<typename T>             vector<T>& operator++            (vector<T> &v){for (auto& i : v) ++i;            return  v;}
template<typename T>             istream& operator>>(istream& is,  vector<T> &v){for (auto& i : v) is >> i;        return is;}
template<typename T>             ostream& operator<<(ostream& os,  vector<T>  v){for (auto& i : v) os << i << ' '; return os;}
template<typename T, typename U> pair<T,U>& operator--           (pair<T, U> &p){--p.first; --p.second;            return  p;}
template<typename T, typename U> pair<T,U>& operator++           (pair<T, U> &p){++p.first; ++p.second;            return  p;}
template<typename T, typename U> istream& operator>>(istream& is, pair<T, U> &p){is >> p.first >> p.second;        return is;}
template<typename T, typename U> ostream& operator<<(ostream& os, pair<T, U>  p){os << p.first << ' ' << p.second; return os;}
template<typename T, typename U> pair<T,U> operator-(pair<T,U> a, pair<T,U> b){return mp(a.first-b.first, a.second-b.second);}
template<typename T, typename U> pair<T,U> operator+(pair<T,U> a, pair<T,U> b){return mp(a.first+b.first, a.second+b.second);}
template<typename T, typename U> void umin(T& a, U b){if (a > b) a = b;}
template<typename T, typename U> void umax(T& a, U b){if (a < b) a = b;}

#ifdef HOME
#define SHOW_COLORS
#include "/mnt/c/Libs/tools/print.cpp"
#else
#define show(...) void(0)
#define debugf(fun)   fun
#define debugv(var)   var
#define mclock    void(0)
#define shows     void(0)
#define debug  if (false)
#define OSTREAM(...)    ;
#define OSTREAM0(...)   ;
#endif

template<class Fun>
class y_combinator_result {
    Fun fun_;
public:
    template<class T>
    explicit y_combinator_result(T &&fun): fun_(std::forward<T>(fun)) {}

    template<class ...Args>
    decltype(auto) operator()(Args &&...args) {
        return fun_(std::ref(*this), std::forward<Args>(args)...);
    }
};
template<class Fun>
decltype(auto) y_combinator(Fun &&fun) {
    return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun));
}
// auto gcd = std::y_combinator([](auto gcd, int a, int b) -> int {
//     return b == 0 ? a : gcd(b, a % b);
// });

void test_case(int test) {
    int n, m;
    cin >> n >> m;
    vector<bool> special(n + 1, false);
    vector<vector<int>> g(n + 1);
    for (int i = 0; i < n; ++i) {
        int a;
        cin >> a;
        g[a].pb(i + 1);
    }
    for (int i = 0; i < m; ++i) {
        int k;
        cin >> k;
        special[k] = true;
    }

    vector<deque<char>> dp(g.size());

    auto cmp = [&](int i, int j) {
        int s = min(dp[i].size(), dp[j].size());
        for (int k = 0; k < s; ++k) {
            if (dp[i][k] != dp[j][k])
                return dp[i][k] < dp[j][k] ? -1 : 1;
        }
        if (dp[i].size() != dp[j].size())
            return dp[i].size() > dp[j].size() ? -1 : 1;
        return 0;
    };

    string ans(n + 1, '.');

    y_combinator([&](auto dfs, int v) -> int {
        if (g[v].empty()) {
            assert(special[v]);
            dp[v].pb(0);
            return v;
        }

        vector<pair<int, int>> cur;
        for (int k : g[v]) {
            cur.eb(k, dfs(k));
        }

        sort(cur.begin(), cur.end(), [&](auto a, auto b) {
            int c = cmp(a.second, b.second);
            if (c != 0) return c < 0;
            return a.first < b.first;
        });

        int i0 = 0;
        for (int i = 1; i < cur.size(); ++i)
            if (dp[cur[i].second].size() > dp[cur[i0].second].size())
                i0 = i;

        int ret = cur[i0].second;
        dp[ret].pb(2);
        dp[ret].push_front(1);
        for (int i = i0 + 1; i < cur.size(); ++i) {
            dp[ret].pb(1);
            for (char c : dp[cur[i].second])
                dp[ret].pb(c);
            dp[ret].pb(2);
        }
        for (int i = i0 - 1; i >= 0; --i) {
            dp[ret].push_front(2);
            reverse(dp[cur[i].second].begin(), dp[cur[i].second].end());
            for (char c : dp[cur[i].second])
                dp[ret].push_front(c);
            dp[ret].push_front(1);
        }

        if (special[v])
            dp[ret].push_front(0);

        for (int i = 0; i < cur.size(); ++i) {
            ans[cur[i].first] = 'a' + i;
            if (i != i0) {
                dp[cur[i].second].clear();
                dp[cur[i].second].shrink_to_fit();
            }
        }

        return ret;
    })(0);

    cout << ans.substr(1) << '\n';
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);

    int T;
    cin >> T;
    for (int test = 1; test <= T; ++test) {
        test_case(test);
    }

    return 0;
}