/**POJ 1860 Currency Exchange*判断回路是否能使初始值增长*/#include <cstdio>#include <cstring>#include <queue>using namespace std;#define INF 0x3f3f3f3f#define MAXN 600struct ArcNode {	int to;	double r;	double c;	ArcNode *next;};queue<int> q;int N, M, S;double V;ArcNode *list[MAXN]; //每个顶点的边链表表头指针bool visit[MAXN];  //每个顶点是否在队列int count[MAXN]; //每个顶点入队列的次数double dist[MAXN];bool spfa(int src){	int i, u, v;	ArcNode *temp;	for (i = 1 ; i <= N; i++) {		dist[i] = 0;	}	dist[src] = V;	q.push(src);	while ( !q.empty()) {		if(dist[src] > V)	return true;		u = q.front();		q.pop();		temp = list[u];		while (temp != NULL) {			v = temp->to;			if (dist[v] < (dist[u] - temp->c) * temp->r) {				dist[v] = (dist[u] - temp->c) * temp->r;				if (!visit[v]) {					q.push(v);  visit[v] = 1;				}				count[v]++;				if (count[v] > N) //存在回路					return true;			}			temp = temp->next;		}		visit[u] = 0;	}	return false;}int main(){	int i, T;	int u, v;	double r, c;	while (~scanf("%d %d %d %lf", &N, &M, &S, &V)) {		memset(list, 0, sizeof(list));		memset(visit, 0, sizeof(visit));		memset(count, 0, sizeof(count));		while (!q.empty()) {			q.pop();		}		ArcNode *temp;		for (i = 0; i < M; i++) {			scanf("%d %d %lf %lf", &u, &v, &r, &c);			temp = new ArcNode;			temp->to = v;   temp->r = r;    temp->c = c;    temp->next = NULL;			if (list[u] == NULL) {				list[u] = temp;			} else {				temp->next = list[u];   list[u] = temp;			}			scanf("%lf %lf", &r, &c);			temp = new ArcNode;			temp->to = u;   temp->r = r;    temp->c = c;    temp->next = NULL;			if (list[v] == NULL) {				list[v] = temp;			} else {				temp->next = list[v];   list[v] = temp;			}		}		if (spfa(S)) {			printf("YES\n");		} else {			printf("NO\n");		}		for (i = 1; i <= N; i++) {			temp = list[i];			while (temp != NULL) {				list[i] = temp->next;   delete temp;    temp = list[i];			}		}	}	return 0;}