#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>using namespace std;typedef long long LL;const int maxn = 20000 + 5;const int maxm = 200000 * 30;const LL INF = INT_MAX - 2;int first[maxn],nxt[maxm],v[maxm],cap[maxm];int n,m,s,t,ans,ecnt;inline void adde(int uu,int vv,int ww) {    v[ecnt] = vv; cap[ecnt] = ww;    nxt[ecnt] = first[uu];    first[uu] = ecnt++;    v[ecnt] = uu; cap[ecnt] = 0;    nxt[ecnt] = first[vv];    first[vv] = ecnt++;}inline void input() {    int a,b,c;    for(int i = 1;i <= n;i++) {        scanf("%d%d",&a,&b);        adde(s,i,a); adde(i,t,b);    }    for(int i = 1;i <= m;i++) {        scanf("%d%d%d",&a,&b,&c);        adde(a,b,c);        adde(b,a,c);    }}int q[maxn * 2],qs,qe,level[maxn];inline bool bfs() {    qs = qe = 0;    memset(level,0,sizeof level);    q[qe++] = s;    level[s] = 1;    while(qs < qe) {        int now = q[qs++];        if(now == t) break;        for(int i = first[now];~i;i = nxt[i]) {            if(!level[v[i]] && cap[i]) {                level[v[i]] = level[now] + 1;                q[qe++] = v[i];            }        }    }    return level[t];}int dfs(int now,int alpha) {    if(now == t) return alpha;    int sum = 0;    for(int i = first[now];~i && alpha;i = nxt[i]) {        if(level[v[i]] == level[now] + 1 && cap[i]) {            int ret = dfs(v[i],min(alpha,cap[i]));            cap[i] -= ret; cap[i ^ 1] += ret;            sum += ret; alpha -= ret;        }    }    if(sum == 0) level[now] = -1;    return sum;}inline int dinic() {    int ans = 0;    while(bfs()) ans += dfs(s,INF);    return ans;}inline void solve() {    int ret = dinic();    printf("%d\n",ret);}int main() {    while(scanf("%d%d",&n,&m) != EOF) {        ecnt = 0;        s = 0; t = n + 1;        memset(first,-1,sizeof(first));        input();        solve();    }    return 0;}