1 #include <iostream>
 2 #include <cstring>
 3 #include <algorithm>
 4 #define MAXVERTEXNUM 500
 5 #define INF 1000000
 6 using namespace std;
 7
 8 struct E
 9 {
10     int a, b;
11     double exchange_currency, tips;
12 }Edge[MAXVERTEXNUM];
13 int Nv, Ne, s, num = 0;
14 double org, dist[MAXVERTEXNUM];
15
16 bool Bellman_Ford()
17 {
18     for (int i = 1; i < Nv; ++i)
19     {
20         bool flag = false;
21         for (int j = 0; j < num; ++j)
22         {
23             if (dist[Edge[j].b] < (dist[Edge[j].a] - Edge[j].tips) * Edge[j].exchange_currency)
24             {
25                 dist[Edge[j].b] = (dist[Edge[j].a] - Edge[j].tips) * Edge[j].exchange_currency;
26                 flag = true;
27             }
28         }
29         if (!flag)
30             return false;//写break还要快一些，黑人问号？？？
31     }
32
33     for (int i = 0; i < num; ++i)
34         if (dist[Edge[i].b] < (dist[Edge[i].a] - Edge[i].tips) * Edge[i].exchange_currency)
35             return true;
36
37     return false;
38 }
39
40 int main()
41 {
42     ios::sync_with_stdio(false);
43
44     cin >> Nv >> Ne >> s >> org;
45     memset(dist, 0, sizeof(dist));
46     dist[s] = org;
47     //init
48
49     for (int i = 1; i <= Ne; ++i)
50     {
51         int V1, V2;
52         double t1, t2, t3, t4;
53         cin >> V1 >> V2 >> t1 >> t2 >> t3 >> t4;
54         Edge[num].a = V1, Edge[num].b = V2;
55         Edge[num].exchange_currency = t1;
56         Edge[num++].tips = t2;
57         Edge[num].a = V2, Edge[num].b = V1;
58         Edge[num].exchange_currency = t3;
59         Edge[num++].tips = t4;
60     }
61
62     if (Bellman_Ford())
63         cout << "YES" << endl;
64     else
65         cout << "NO" << endl;
66
67     return 0;
68 }