#include<iostream>
#include<cstdio>
#include<vector>
using namespace std;
vector<int>F,M;
int N,D;
long long Ans=0;
int main()
{
	freopen("optmilk.in","r",stdin);
	freopen("optmilk.out","w",stdout);
	ios::sync_with_stdio(false);
	int i,j,k,m;
	cin>>N>>D;
	M.resize(N);
	F.resize(N+1);
	for(i=0;i<N;i++)
		cin>>M[i];
	F[0]=0;F[1]=M[0];
	for(i=0;i<D;i++)
	{
		cin>>k>>m;
		M[k-1]=m;
		F[0]=0;F[1]=M[0];
		for(j=2;j<=N;j++)
			F[j]=max(F[j-1],F[j-2]+M[j]);
		Ans+=F[N];
	}
	cout<<Ans;
	return 0;
}