#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
typedef pair<int,int> pii;
typedef long long ll;
typedef double ld;
typedef vector<int> vi;
#define fi first
#define se second
#define fe first
#define FO(x) {freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);}
#define Edg int M=0,fst[SZ],vb[SZ],nxt[SZ];void ad_de(int a,int b){++M;nxt[M]=fst[a];fst[a]=M;vb[M]=b;}void adde(int a,int b){ad_de(a,b);ad_de(b,a);}
#define Edgc int M=0,fst[SZ],vb[SZ],nxt[SZ],vc[SZ];void ad_de(int a,int b,int c){++M;nxt[M]=fst[a];fst[a]=M;vb[M]=b;vc[M]=c;}void adde(int a,int b,int c){ad_de(a,b,c);ad_de(b,a,c);}
#define es(x,e) (int e=fst[x];e;e=nxt[e])
#define esb(x,e,b) (int e=fst[x],b=vb[e];e;e=nxt[e],b=vb[e])
#define SZ 2000999
int n,k,w[SZ],c[SZ],d[SZ],mi[11],mx[11],wd[SZ][11],po[222];
ll rv[222];
const int MOD=1e9+7;
ll qp(ll a,ll b)
{
	ll x=1;a%=MOD;
	while(b)
	{
		if(b&1) x=x*a%MOD;
		a=a*a%MOD; b>>=1;
	}
	return x;
}
ll ap[233][33],rt[233]; int an=0;
int main()
{
//	FO(walk)
	scanf("%d%d",&n,&k);
	for(int i=1;i<=k;++i) scanf("%d",w+i);
	for(int i=1;i<=n;++i) scanf("%d%d",c+i,d+i);
	for(int i=1;i<=n*2;++i) c[i+n]=c[i],d[i+n]=d[i];
	for(int i=1;i<=n*3;++i)
	{
		po[c[i]]+=d[i];
		for(int j=1;j<=k;++j)
			mi[j]=min(mi[j],po[j]),
			mx[j]=max(mx[j],po[j]);
		for(int j=1;j<=k;++j)
			wd[i][j]=mx[j]-mi[j];
	}
	{
	int w=k+2;
	for(int j=0;j<w;++j)
	{
		ll p=1;
		for(int k=0;k<w;++k)if(j!=k)p=p*(j-k)%MOD;
		rv[j]=qp(p,MOD-2);
	}
	}
	ll ans=1;
	map<ll,int> id;
	for(int i=1;i<=k;++i) ans=ans*w[i]%MOD;
	for(int i=1;i<=n+n;++i)
	{
		int dx[14],dt[14];
		ll f[14];
		ll f1=1;
		for(int j=1;j<=k;++j)
			f1=f1*(dx[j]=max(w[j]-wd[i][j],0))%MOD;
		if(!f1) continue;
		if(i<=n)
		{
			ans+=f1;ans%=MOD;
			continue;
		}
		bool eq=1;
		for(int j=1;j<=k;++j)
		{
			eq&=wd[i][j]==wd[i+n][j],
			dt[j]=wd[i+n][j]-wd[i][j];
		}
		if(eq&&f1)
		{
			puts("-1");
			return 0;
		}
		//sum u prod (dx[j]-dt[j]*u)
		//apparently it's a polynomial
		int mx=2e9;
		for(int j=1;j<=k;++j)
			if(dt[j]) mx=min(mx,dx[j]/dt[j]);
		int&ig=id[mx];
		if(!ig) ig=++an,rt[an]=mx;
		int w=k+2;
		ll su=0;
		for(int j=0;j<w;++j)
		{
			ll p=1;
			for(int t=k;t;--t)
				p=p*(dx[t]-dt[t]*j)%MOD;
//			cout<<p<<",";
			(su+=p)%=MOD; (ap[ig][j]+=su)%=MOD;
		}
	}
	for(int i=1;i<=an;++i)
	{
		int mx=rt[i],w=k+2;
		ll qz[15],hz[15];
		qz[0]=1;
		for(int p=0;p<w;++p)
			qz[p+1]=qz[p]*(mx-p)%MOD;
		hz[w]=1;
		for(int p=w;p;--p)
			hz[p-1]=hz[p]*(mx-p+1)%MOD;
		for(int j=0;j<w;++j)
			(ans+=ap[i][j]*rv[j]%MOD*qz[j]%MOD*hz[j+1])%=MOD;
	}
	ans=(ans%MOD+MOD)%MOD;
	cout<<ans<<"\n";
}