1 #include<cstdio>
 2 #include<cctype>
 3 #include<vector>
 4 #include<functional>
 5 #include<ext/pb_ds/priority_queue.hpp>
 6 inline int getint() {
 7     register char ch;
 8     while(!isdigit(ch=getchar()));
 9     register int x=ch^'0';
10     while(isdigit(ch=getchar())) x=(((x<<2)+x)<<1)+(ch^'0');
11     return x;
12 }
13 const int inf=0x7fffffff;
14 const int V=101,W=101;
15 struct Edge {
16     int to,w1,w2;
17 };
18 std::vector<Edge> e[V];
19 inline void add_edge(const int &u,const int &v,const int &w1,const int &w2) {
20     e[u].push_back((Edge){v,w1,w2});
21 }
22 int n,m,s,t;
23 struct Vertex {
24     int dis,id,w;
25     bool operator > (const Vertex &another) const {
26         return dis>another.dis;
27     }
28 };
29 int d[V][(V-1)*W];
30 __gnu_pbds::priority_queue<Vertex,std::greater<Vertex>> q;
31 __gnu_pbds::priority_queue<Vertex,std::greater<Vertex>>::point_iterator p[V][V*W];
32 inline void dijkstra() {
33     for(register int i=1;i<=n;i++) {
34         for(register int j=0;j<(n-1)*W;j++) {
35             p[i][j]=q.push((Vertex){d[i][j]=(i==s&&j==0)?0:inf,i,j});
36         }
37     }
38     while(q.top().dis!=inf) {
39         const Vertex x=q.top();
40         for(register unsigned i=0;i<e[x.id].size();i++) {
41             const Edge &y=e[x.id][i];
42             if((x.w+y.w1)<(n-1)*W&&(x.dis+y.w2)<d[y.to][x.w+y.w1]) {
43                 q.modify(p[y.to][x.w+y.w1],(Vertex){d[y.to][x.w+y.w1]=x.dis+y.w2,y.to,x.w+y.w1});
44             }
45         }
46         q.modify(p[x.id][x.w],(Vertex){inf,x.id,x.w});
47     }
48     q.clear();
49 }
50 int main() {
51     n=getint(),m=getint(),s=getint(),t=getint();
52     for(register int i=1;i<=m;i++) {
53         int u=getint(),v=getint(),t=getint(),c=getint();
54         add_edge(u,v,t,c);
55         add_edge(v,u,t,c);
56     }
57     dijkstra();
58     int ans=0,min=inf;
59     for(register int i=0;i<(n-1)*W;i++) {
60         if(d[t][i]==inf) continue;
61         if(d[t][i]<min) {
62             ans++;
63             min=d[t][i];
64         }
65     }
66     printf("%d\n",ans);
67     return 0;
68 }