#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
  
//#include <map>
#include <set>
#include <queue>
#include <string>
#include <iostream>
#include <algorithm>
  
using namespace std;
  
#define maxn 50005
#define ll long long
#define me 400005
#define inf 0x3f3f3f3f
#define F(i,j,k) for (int i=j;i<=k;++i)
#define D(i,j,k) for (int i=j;i>=k;--i)
  
void Finout()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
    #endif
}
  
int Getint()
{
    int x=0,f=1; char ch=getchar();
    while (ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) f=-1; ch=getchar();}
    while (ch>=‘0‘&&ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
    return x*f;
}
int h[me<<1],to[me<<1],ne[me<<1],fl[me<<1],en=0,S=0,T=me-1;
   
void add(int a,int b,int c)
{
    to[en]=b; ne[en]=h[a]; fl[en]=c; h[a]=en++;
//    to[en]=a; ne[en]=h[b]; fl[en]=0; h[b]=en++;
}
 
int map[me];
   
bool tell()
{
    queue <int> q;
    memset(map,-1,sizeof map);
    map[S]=0;
    while (!q.empty()) q.pop();
    q.push(S);
    while (!q.empty())
    {
        int x=q.front(); q.pop();
        for (int i=h[x];i>=0;i=ne[i])
        {
            if (map[to[i]]==-1&&fl[i]>0)
            {
                map[to[i]]=map[x]+1;
                q.push(to[i]);
            }
        }
    }
    if (map[T]!=-1) return true;
    return false;
}
   
int zeng(int k,int r)
{
    if (k==T) return r;
    int ret=0;
    for (int i=h[k];i>=0&&ret<r;i=ne[i])
        if (map[to[i]]==map[k]+1&&fl[i]>0)
        {
            int tmp=zeng(to[i],min(fl[i],r-ret));
            ret+=tmp; fl[i]-=tmp; fl[i^1]+=tmp;
        }
    if (!ret) map[k]=-1;
    return ret;
}
 
int main()
{
    memset(h,-1,sizeof h);
    Finout();
    int n,m,a,b,c;
    n=Getint();m=Getint();
    F(i,1,n)
    {
        a=Getint(); b=Getint();
        add(S,i,a);
        add(i,S,0);
        add(i,T,b);
        add(T,i,0);
    }
    F(i,1,m)
    {
        a=Getint(); b=Getint();
        c=Getint();
        add(a,b,c);
        add(b,a,c);
    }
    int ans=0,tmp;
    while (tell()) while (tmp=zeng(S,inf)) ans+=tmp;
    cout<<ans<<endl;
}