#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

#define rep(i,n) for(ll i=0;i<n;++i)
#define all(a) (a).begin(),(a).end()
ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll modpow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
template<class T> T div_floor(T a, T b) { return a / b - ((a ^ b) < 0 && a % b); }
template<class T> T div_ceil(T a, T b) { return a / b + ((a ^ b) > 0 && a % b); }
template <typename T, typename U> inline bool chmin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template <typename T, typename U> inline bool chmax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
ostream &operator<<(ostream &os,mint a){return os<<a.val();}
template<typename T,typename U>
ostream &operator<<(ostream &os,const pair<T,U> &p){
    return os<<p.first<<' '<<p.second;
}

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &a){
    if (a.empty()) return os;
    os << a.front();
    for (auto e : a | views::drop(1)){
        os << ' ' << e;
    }
    return os;
}

void dump(auto ...vs){
    ((cout << vs << ' '), ...) << endl;
}



void solve() {
    ll N,M;
    cin>>N>>M;
    ll src=N;
    ll tar=src+1;
    mf_graph<ll> mf(tar+1);
    ll get=0;
    rep(i,N){
        ll a,b;
        cin>>a>>b;
        get+=a+b;
        mf.add_edge(src,i,a);
        mf.add_edge(i,tar,b);
    }
    rep(i,M){
        ll u,v,c;
        cin>>u>>v>>c;
        u--;
        v--;
        mf.add_edge(u,v,c);
        mf.add_edge(v,u,c);
    }
    ll f=mf.flow(src,tar);
    ll ans=get-f;
    cout<<ans<<'\n';
    return;
}


int main() {
    cin.tie(0)->sync_with_stdio(0);
    ll T=1;
    while (T--){
        solve();
    }
    return 0;
}