# 1238 파티

www.acmicpc.net/problem/1238

1238번: 파티

import heapq
import sys
input = sys.stdin.readline 

n, m, x = map(int,input().split())
# n 명, 도로 m 개 , x 마을에서 

graph= [ [] for i in range(n+1)]
for i in range(m):
  a,b,c = map(int,input().split())
  graph[a].append((b,c))

def dij(start):
  q = []
  heapq.heappush(q, (0,start))
  dist = [1e9]*(n+1)
  dist[start] = 0 

  while q:
    d, now = heapq.heappop(q)
    if dist[now]<d : continue 
    for i in graph[now]:
      cost = d + i[1]
      if cost < dist[i[0]]:
        dist[i[0]] = cost 
        heapq.heappush(q,(cost,i[0]))
  return dist 

result = [0]
dist_x = dij(x)
for i in range(1,n+1):
  result.append( dij(i)[x] + dist_x[i] ) 

print ( max(result) )