from collections import deque
 
def nearest_meeting_cell(n, edges, c1, c2):
    def bfs(start):
        """Performs BFS from the start cell and returns a dictionary of distances."""
        distances = {}
        queue = deque([(start, 0)])
        visited = set()
 
        while queue:
            node, dist = queue.popleft()
            if node in visited:
                continue
            visited.add(node)
            distances[node] = dist
            # Move to the next node if it exists and hasn't been visited
            next_node = edges[node]
            if next_node != -1 and next_node not in visited:
                queue.append((next_node, dist + 1))
 
        return distances
 
    # Get reachable distances from both C1 and C2
    dist_from_c1 = bfs(c1)
    dist_from_c2 = bfs(c2)
 
    # Find common cells that are reachable from both
    common_cells = set(dist_from_c1.keys()) & set(dist_from_c2.keys())
 
    if not common_cells:
        return -1  # No meeting cell
 
    # Find the nearest meeting cell
    nearest_cell = -1
    min_distance = float('inf')
 
    for cell in common_cells:
        total_distance = max(dist_from_c1[cell], dist_from_c2[cell])
        if total_distance < min_distance:
            min_distance = total_distance
            nearest_cell = cell
 
    return nearest_cell
 
# Input reading
n = int(input())  # Number of cells
edges = list(map(int, input().split()))  # Edges array
c1, c2 = map(int, input().split())  # Two cells to check
 
# Output the nearest meeting cell
print(nearest_meeting_cell(n, edges, c1, c2))

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4 4 1 4 13 8 8 8 0 8 14 9 15 11 -1 10 15 22 22 22 22 22 21
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