#include <bits/stdc++.h>
using namespace std;
#if __has_include("all.hpp")
#include "all.hpp"
#else
#include <atcoder/all>
#endif
using namespace atcoder;
int main(void){
    int n,m;
    cin>>n>>m;
    mf_graph<long long> g(n+2);
    long long ans=0;
    for(int i=0;i<n;i++){
        int a,b;
        cin>>a>>b;
        ans+=a+b;
        g.add_edge(n,i,a);
        g.add_edge(i,n+1,b);
    }
    for(int i=0;i<m;i++){
        int a,b,c;
        cin>>a>>b>>c;
        g.add_edge(a-1,b-1,c);
    }
    cout<<ans-g.flow(n,n+1)<<endl;
    return 0;
}