1 #include<queue>
2 #include<cstdio>
3 #include<cstring>
4 #include<algorithm>
5 using namespace std;
6 int n,m,cnt,tot;
7 int st,ed;
8 int dx[8]={1,1,-1,-1,2,2,-2,-2};
9 int dy[8]={2,-2,2,-2,1,-1,1,-1};
10 int head[80005];
11 int cur[80005];
12 int dis[80005];
13 struct node{
14 int fr;
15 int to;
16 int nxt;
17 int flw;
18 }edge[1000005];
19 void init(){
20 memset(head,-1,sizeof(head));
21 }
22 void addedge(int u,int v,int f){
23 edge[cnt].fr=u;
24 edge[cnt].to=v;
25 edge[cnt].flw=f;
26 edge[cnt].nxt=head[u];
27 head[u]=cnt++;
28 edge[cnt].fr=v;
29 edge[cnt].to=u;
30 edge[cnt].flw=0;
31 edge[cnt].nxt=head[v];
32 head[v]=cnt++;
33 }
34 bool bfs(){
35 queue<int>que;
36 memset(dis,0x3f,sizeof(dis));
37 que.push(st);dis[st]=0;
38 while(!que.empty()){
39 int u=que.front();
40 que.pop();
41 for(int i=head[u];i!=-1;i=edge[i].nxt){
42 if(!edge[i].flw)continue;
43 int v=edge[i].to;
44 if(dis[v]==0x3f3f3f3f){
45 dis[v]=dis[u]+1;
46 que.push(v);
47 }
48 }
49 }
50 return (dis[ed]!=0x3f3f3f3f);
51 }
52 int dfs(int u,int flw){
53 int All=0;int tmp;
54 if(u==ed)return flw;
55 for(int i=head[u];i!=-1;i=edge[i].nxt){
56 if(!edge[i].flw)continue;
57 int v=edge[i].to;head[u]=i;
58 if(dis[v]!=dis[u]+1)continue;
59 if((tmp=dfs(v,min(flw,edge[i].flw)))>0){
60 flw-=tmp;
61 edge[i].flw-=tmp;
62 edge[i^1].flw+=tmp;
63 All+=tmp;
64 if(!flw)break;
65 }
66 }
67 return All;
68 }
69 int dicnic(){
70 scanf("%d%d%d%d",&n,&m,&st,&ed);
71 int ret=0;
72 for(int i=1;i<=m;i++){
73 int u,v,w;
74 scanf("%d%d%d",&u,&v,&w);
75 addedge(u,v,w);
76 }
77 memcpy(cur,head,sizeof(cur));
78 while(bfs()){
79 ret+=dfs(st,0x3f3f3f3f);
80 memcpy(head,cur,sizeof(head));
81 }
82 return ret;
83 }
84 int main(){
85 init();
86 printf("%d\n",dicnic());
87 return 0;
88 }
