1 #include <iostream>
2 #include <string.h>
3 #include <stdio.h>
4 #include <algorithm>
5 #include <queue>
6 #define V 10100
7 #define E 1000100
8 #define inf 99999999
9 using namespace std;
10 int vis[V];
11 int dist[V];
12 int pre[V];
13
14 struct Edge{
15 int u,v,c,cost,next;
16 }edge[E];
17 int head[V],cnt;
18
19 void init(){
20 cnt=0;
21 memset(head,-1,sizeof(head));
22 }
23 void addedge(int u,int v,int c,int cost)
24 {
25 edge[cnt].u=u;edge[cnt].v=v;edge[cnt].cost=cost;
26 edge[cnt].c=c;edge[cnt].next=head[u];head[u]=cnt++;
27
28 edge[cnt].u=v;edge[cnt].v=u;edge[cnt].cost=-cost;
29 edge[cnt].c=0;edge[cnt].next=head[v];head[v]=cnt++;
30 }
31
32 bool spfa(int begin,int end){
33 int u,v;
34 queue<int> q;
35 for(int i=0;i<=end+2;i++){
36 pre[i]=-1;
37 vis[i]=0;
38 dist[i]=inf;
39 }
40 vis[begin]=1;
41 dist[begin]=0;
42 q.push(begin);
43 while(!q.empty()){
44 u=q.front();
45 q.pop();
46 vis[u]=0;
47 for(int i=head[u];i!=-1;i=edge[i].next){
48 if(edge[i].c>0){
49 v=edge[i].v;
50 if(dist[v]>dist[u]+edge[i].cost){
51 dist[v]=dist[u]+edge[i].cost;
52 pre[v]=i;
53 if(!vis[v]){
54 vis[v]=true;
55 q.push(v);
56 }
57 }
58 }
59 }
60 }
61 return dist[end]!=inf;
62 }
63
64 int MCMF(int begin,int end){
65 int ans=0,flow;
66 int flow_sum=0;
67 while(spfa(begin,end)){
68 flow=inf;
69 for(int i=pre[end];i!=-1;i=pre[edge[i].u])
70 if(edge[i].c<flow)
71 flow=edge[i].c;
72 for(int i=pre[end];i!=-1;i=pre[edge[i].u]){
73 edge[i].c-=flow;
74 edge[i^1].c+=flow;
75 }
76 ans+=dist[end];
77 flow_sum += flow;
78 }
79 //cout << flow_sum << endl;
80 return ans;
81 }
82
83 int main()
84 {
85 //freopen("in.txt","r",stdin);
86 int n,m,a,b,c;
87 while(scanf("%d%d",&n,&m)!=EOF){
88 init();
89 addedge(0,1,2,0);
90 addedge(n,n+1,2,0);
91 for(int i=1;i<=m;i++){
92 scanf("%d%d%d",&a,&b,&c);
93 addedge(a,b,1,c);
94 addedge(b,a,1,c);
95 }
96 printf("%d\n",MCMF(0,n+1));
97 }
98 return 0;
99 }
