# -*- coding: utf-8 -*-
def deikstra(start_node, finish_node, length, matrix):
    result = 0
    current_node = start_node
    distance = {str(i): float('inf') for i in range(1, length + 1)}
    visited = []
    state = [0]*(length + 1) # состоние 1 - подъем 0 - опускание
    distance[str(current_node)] = 0
    while finish_node not in visited:
        visited.append(current_node)
        for arr in matrix[current_node]:
            n = arr[0]
            w = arr[1]
            if n in visited:
                continue
            if distance[str(current_node)] + abs(state[current_node] - w) < distance[str(n)]:
                diff = 0 if current_node == start_node else abs(state[current_node] - w)
                distance[str(n)] = distance[str(current_node)] + diff
                state[n] = w
        minWeight = 19000000
        for i in range(1, length + 1):
            if (i not in visited) and (distance[str(i)] < minWeight):
                current_node = i
                minWeight = distance[str(i)]
    return distance[str(finish_node)]

n, m = [int(i) for i in input().split()] # n - кол-во вершин, m - кол-во ребер
graph = {}
for i in range(m):
    first, last = [int(i) for i in input().split()]
    if first not in graph:
        graph[first] = []
    if last not in graph:
        graph[last] = []
    graph[first].append([last, 1])
    graph[last].append([first, 0])
start_node, last_node = [int(i) for i in input().split()]
print(deikstra(start_node, last_node, n, graph))