1 #include<cstdio>

 2 #include<cstdlib>

 3 #include<cstring>

 4 #include<iostream>

 5 #include<queue>

 6 using namespace std;

 7

 8 const int N=10010,M=100010,INF=(int)1e9;

 9 int n,m,st,ed,len=1;

10 int last[N],d[N];

11 struct edge{int y,fl,next;}a[2*M];

12 queue<int> q;

13

14 int mmin(int x,int y) {return x<y?x:y;}

15 void ins(int x,int y,int fl)

16 {

17     a[++len].y=y,a[len].fl=fl;

18     a[len].next=last[x],last[x]=len;

19     a[++len].y=x,a[len].fl=0;

20     a[len].next=last[y],last[y]=len;

21 }

22 bool bfs()

23 {

24     while (!q.empty()) q.pop();

25     memset(d,-1,sizeof(d));

26     q.push(st); d[st]=1;

27     while (!q.empty())

28     {

29       int x=q.front(); q.pop();

30       for (int i=last[x];i!=-1;i=a[i].next)

31       {

32         int y=a[i].y;

33         if (!a[i].fl || d[y]!=-1) continue;

34         d[y]=d[x]+1; q.push(y);

35       }

36     }

37     return (d[ed]!=-1);

38 }

39 int dfs(int x,int flow)

40 {

41     if (x==ed) return flow;

42     int sum=0;

43     for (int i=last[x];i!=-1;i=a[i].next)

44     {

45       int y=a[i].y;

46       if (d[y]!=d[x]+1 || !a[i].fl) continue;

47       int p=mmin(a[i].fl,flow-sum);

48       int tmp=dfs(y,p);

49       sum+=tmp;

50       a[i].fl-=tmp,a[i^1].fl+=tmp;

51       if (sum==flow) break;

52     }

53     if (!sum) d[x]=-1;

54     return sum;

55 }

56 int Max_flow()

57 {

58     int sum=0,p;

59     while (bfs())

60       while (p=dfs(st,INF)) sum+=p;

61     return sum;

62 }

63 int main()

64 {

65     scanf("%d%d%d%d",&n,&m,&st,&ed);

66     int x,y,d;

67     memset(last,-1,sizeof(last));

68     for (int i=1;i<=m;i++)

69     {

70       scanf("%d%d%d",&x,&y,&d);

71       ins(x,y,d);

72     }

73     printf("%d\n",Max_flow());

74     return 0;

75 }