1 #include <iostream> 2 #include <math.h> 3 #include <algorithm> 4 #include <cstdio> 5 #include <cstring> 6 #define MAXN 520 7 #define MAXM 6000 8 #define INF 0Xffffff 9 using namespace std ; 10 struct node 11 { 12 int u, v; 13 double rate,cost; 14 } edge[MAXM]; 15 int T, n, m, l, u, w; 16 double dis[MAXN]; 17 int ans; 18 double V; 19 int bellman() 20 { 21 for(int i=0; i<n; i++) 22 dis[i] = 0; 23 dis[l] = V; 24 25 for(int i=0; i<n; i++) 26 { 27 int flag = 0; 28 for(int j=0; j<ans; j++) 29 { 30 if(dis[edge[j].v]<(dis[edge[j].u]-edge[j].cost)*edge[j].rate) 31 { 32 dis[edge[j].v]=(dis[edge[j].u]-edge[j].cost)*edge[j].rate; 33 flag = 1; 34 } 35 } 36 if(!flag) 37 break; 38 39 if(i==n-1) 40 return 1; 41 } 42 return 0; 43 44 45 } 46 void add(int A,int B,double C,double D) 47 { 48 edge[ans].u = A; 49 edge[ans].v = B; 50 edge[ans].rate = C; 51 edge[ans].cost = D; 52 ans++; 53 } 54 int main() 55 { 56 int A,B; 57 double Rab,Cab,Rba,Cba; 58 while(scanf("%d %d %d %lf", &n, &m, &l,&V)!=EOF) 59 { 60 ans = 0; 61 62 for(int i=0; i<m; i++) 63 { 64 scanf("%d%d%lf%lf%lf%lf", &A,&B,&Rab,&Cab,&Rba,&Cba); 65 add(A, B, Rab,Cab); 66 add(B, A, Rba,Cba); 67 } 68 69 70 if(!bellman()) printf("NO "); 71 else printf("YES "); 72 } 73 74 return 0; 75 }