# Define the tree structure
tree = {
    1: [2, 5, 7],
    2: [3, 4],
    5: [6],
    7: [8, 9]
}

# Perform Depth-First Search (DFS) recursively
def dfs(node, visited):
    if node not in visited:
        print(node)
        visited.add(node)
        if node in tree:
            for neighbor in tree[node]:
                dfs(neighbor, visited)

# Start DFS from the root node (1)
print("Depth-First Search (DFS):")
dfs(1, set())
