#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;

typedef long long LL;

const int N = 5e5 + 5, S = 11, INF = 2e9, P = 1e9 + 7;

int n, K, w[N], C[N], D[N], x[S], mn[S], mx[S], len[S], ans, v[S];
int l[S], s[S][S];

int a[S], ta, b[S], tb, c[S];

void inline mul() {
	memset(c, 0, sizeof c);
	for (int i = 0; i <= ta; i++) {
		for (int j = 0; j <= tb; j++) {
			c[i + j] = (c[i + j] + (LL)a[i] * b[j]) % P;
		}
	}
	memcpy(a, c, sizeof a);
	ta += tb;
}

bool inline check(int x) {
	for (int k = 1; k <= K; k++)
		if (len[k] - (LL)x * abs(v[k]) <= 0) return false;
	return true;
}

int inline power(int a, int b) {
	int res = 1;
	while (b) {
		if (b & 1) res = (LL)res * a % P;
		a = (LL)a * a % P;
		b >>= 1;
	}
	return res;
}


int inline query(int a, int b) {
	int res = 1;
	for (int i = 0; i < b; i++)
		res = (LL)res * (a - i) % P * power(i + 1, P - 2) % P;
	return res;
}

int inline work(int x, int k) {
	if (k == 0) return x;
	int sum = 0, t = x + 1, z = 1;
	for (int j = 1; j <= min(x, k); j++) {
		z = (LL)z * j % P;
		t = (LL)t * power(j + 1, P - 2) % P * (x - j + 1) % P;
		sum = (sum + (LL)s[k][j] * t % P * z) % P;
	}
	return sum;
}

int main() {
	scanf("%d%d", &n, &K);
	for (int i = 1; i <= K; i++) 
		scanf("%d", w + i), len[i] = mx[i] = w[i], mn[i] = 1;
	bool ok = true;
	
	s[0][0] = 1;
	for (int i = 1; i <= K; i++) {
		for (int j = 1; j <= i; j++) {
			s[i][j] = (s[i - 1][j - 1] + (LL)s[i - 1][j] * j) % P;
		}
	}
	
	for (int i = 1; i <= n; i++) {
		scanf("%d%d", C + i, D + i);
		int c = C[i];
		x[c] += D[i];
		if (w[c] - x[c] < mx[c]) mx[c] = w[c] - x[c];
		if (1 - x[c] > mn[c]) mn[c] = 1 - x[c];
		int t = max(mx[c] - mn[c] + 1, 0);
		if (t < len[c]) {
			int u = i;
			for (int j = 1; j <= K; j++)
				if (j != c) {
					if (len[j] <= 0) { u = 0; break; }
					u = (LL)u * len[j] % P;
				}
			ans = (ans + u) % P;
			len[c] = t;
		}
		
	}
	int cnt = 0;
	for (int i = 1; i <= K; i++) cnt += !x[i], v[i] = x[i];
	
	
	if (ok && cnt == K) { puts("-1"); return 0; }
	

	
	for (int i = 1; i <= n; i++) {
		int c = C[i];
		x[c] += D[i];
		if (w[c] - x[c] < mx[c]) mx[c] = w[c] - x[c];
		if (1 - x[c] > mn[c]) mn[c] = 1 - x[c];
		int t = max(mx[c] - mn[c] + 1, 0);
		
		if (t < len[c]) {
			int u = n + i;
			for (int j = 1; j <= K; j++)
				if (j != c) {
					if (len[j] <= 0) { u = 0; break; }
					u = (LL)u * len[j] % P;
				}
			ans = (ans + u) % P;
			memset(a, 0, sizeof a); 
			
			ta = 1;
			a[0] = n + i, a[1] = n;
		
			for (int k = 1; k <= K; k++) {
				if (k != c) {
					tb = 1;
					b[0] = len[k] % P;
					b[1] = (P - abs(v[k])) % P;
					mul();
				}
			
			}
			
			int l = 0, r = 1e9;
			
			while (l < r) {
				int mid = (l + r + 1) >> 1;
				if (check(mid)) l = mid;
				else r = mid - 1;
			}
			
			if (check(r)) {
				for (int j = 0; j <= ta; j++) {
					
					ans = (ans + (LL)a[j] * work(r, j)) % P;
				}
			}
			
			
			
			len[c] = t;
		}
	}
	printf("%d\n", ans);
	return 0;
}