#include<iostream>

#include<cstdio>

#include<cstring>

#include<queue>

using namespace std;

const int N=2e4+,M=2e5+,INF=0x3f3f3f3f;

int n,m,hd[N],cr[N],xnt=,mxflow,dfn[N];

int num;

struct Ed{

  int nxt,to,cap;

  Ed(int n=,int t=,int c=):nxt(n),to(t),cap(c) {}

}ed[(N+M)<<];

void add(int x,int y,int z)

{

  ed[++xnt]=Ed(hd[x],y,z);hd[x]=xnt;

  ed[++xnt]=Ed(hd[y],x,);hd[y]=xnt;

}

bool bfs()

{

  memset(dfn,,sizeof dfn);

  dfn[]=;queue<int> q;q.push();

  while(q.size())

    {

      int k=q.front();q.pop();

      for(int i=hd[k],v;i;i=ed[i].nxt)

    if(!dfn[v=ed[i].to]&&ed[i].cap)

      {

        dfn[v]=dfn[k]+;q.push(v);

        if(v==n+)return true;

      }

    }

  return false;

}

int dinic(int x,int flow)

{

  if(x==n+)return flow;//!!!

  int use=;

  for(int &i=cr[x],v;i;i=ed[i].nxt)

    if(dfn[v=ed[i].to]==dfn[x]+&&ed[i].cap)

      {

    int tmp=dinic(v,min(ed[i].cap,flow-use));

    if(!tmp)dfn[v]=;

    ed[i].cap-=tmp;ed[i^].cap+=tmp;use+=tmp;

    if(use==flow)return flow;

      }

  return use;

}

int main()

{

  scanf("%d%d",&n,&m);int x,y,z;

  for(int i=;i<=n;i++)

    {

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

      add(,i,x);add(i,n+,y);

    }

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

    {

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

      add(x,y,z);add(y,x,z);

    }

  while(bfs())

    {

      memcpy(cr,hd,sizeof hd);

      int k=dinic(,INF);

      mxflow+=k;

    }

  printf("%d",mxflow);

  return ;

}