#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>

using namespace std;

const int MAXN = 105;
const int dx[] = {-1, 0, 0, 1};
const int dy[] = {0, -1, 1, 0};

int T, H, W, label;
int alt[MAXN][MAXN], basin[MAXN][MAXN];
char ans[MAXN][MAXN];
vector<pair<int, int>> sinks;

void dfs(int x, int y) {
    if (basin[x][y] != -1) return;
    int nx = -1, ny = -1, min_alt = alt[x][y];
    for (int i = 0; i < 4; i++) {
        int tx = x + dx[i], ty = y + dy[i];
        if (tx < 0 || tx >= H || ty < 0 || ty >= W) continue;
        if (alt[tx][ty] < min_alt) {
            nx = tx;
            ny = ty;
            min_alt = alt[tx][ty];
        }
    }
    if (nx == -1 && ny == -1) {
        // this cell is a sink
        basin[x][y] = label;
        sinks.emplace_back(x, y);
        return;
    }
    dfs(nx, ny);
    basin[x][y] = basin[nx][ny];
}

void solve() {
    cin >> H >> W;
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            cin >> alt[i][j];
        }
    }
    memset(basin, -1, sizeof(basin));
    label = 0;
    sinks.clear();
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (basin[i][j] == -1) {
                dfs(i, j);
                label++;
            }
        }
    }
    sort(sinks.begin(), sinks.end(), [](const pair<int, int>& a, const pair<int, int>& b) {
        if (alt[a.first][a.second] != alt[b.first][b.second]) {
            return alt[a.first][a.second] < alt[b.first][b.second];
        } else if (a.first != b.first) {
            return a.first < b.first;
        } else {
            return a.second < b.second;
        }
    });
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            ans[i][j] = 'a' + basin[i][j];
        }
    }
    cout << "Case #" << ++T << ":\n";
    for (const auto& p : sinks) {
        ans[p.first][p.second] = 'a' + (int)(distance(sinks.begin(), lower_bound(sinks.begin(), sinks.end(), p)) % 26);
    }
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            cout << ans[i][j] << " ";
        }
        cout << "\n";
    }
}

int main() {
    int tests;
    cin >> tests;
    while (tests--) {
        solve();
    }
    return 0;
}