#include<bits/stdc++.h>
#define Gc() getchar() 
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;using LL=__int128;
const int N=36+5,M=N*40+5,K=(1<<25)+5,mod=998244353,Mod=mod-1;const db eps=1e-9;const ll INF=1e18+7;mt19937 rnd(time(0));
int n,m;ll A[N],B[N];
vector<int> S[N];
struct Node{
	ll x,y;
	Node operator +(const Node &B)const{return (Node){x+max(B.x-(x+y),0ll),y+B.y};}
	bool operator <(const Node &B)const{
		if((y>0)^(B.y>0)) return (y>0)>(B.y>0);
		if(y>0) return x<B.x;
		return x+y>B.x+B.y;
	}
}w[N];
int vis[N];
void Solve(){
	int i,j;scanf("%d%d",&n,&m);
	for(i=2;i<=n;i++) scanf("%lld%lld",&A[i],&B[i]);
	while(m--){int x,y;scanf("%d%d",&x,&y);S[x].emplace_back(y);}
	ll ans=INF;
	while(clock()*1.0/CLOCKS_PER_SEC<6.95){
		Node tot=(Node){0,0};Me(vis,0);
		for(int i:S[1]) vis[i]=1;
		for(i=2;i<=n;i++) {
			vector<pair<Node,int> > pus;
			for(j=2;j<=n;j++) if(vis[j]==1) pus.emplace_back((Node){A[j],B[j]-A[j]},j);
			sort(pus.begin(),pus.end());
			for(j=0;j<pus.size();j++) if(R(2)==1||j+1==pus.size()) {
				int id=pus[j].se;vis[id]=-1;
				// cerr<<id<<'\n';
				for(int h:S[id]) if(!vis[h]) vis[h]=1;
				tot=tot+pus[j].fi;
				break;
			}
		}
		ans=min(ans,tot.x);//break;
	}
	printf("%lld\n",ans);
}
int main(){
	int t;
	// scanf("%d",&t);
	t=1;
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}