#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
int N,D,M[40010];
long long dp[40010];
long long ans=0;
int main()
{
	freopen("optmilk.in","r",stdin);
	freopen("optmilk.out","w",stdout);
	scanf("%d%d",&N,&D);
	for(int i=1;i<=N;i++)
		scanf("%d",&M[i]);
	dp[0]=0;
	dp[1]=M[1];
	for(int i=2;i<=N;i++)
		dp[i]=max(dp[i-2]+M[i],dp[i-1]);
	int k,m;
	for(int day=1;day<=D;day++)
	{
		scanf("%d%d",&k,&m);
		M[k]=m;
		for(int i=k;i<=N;i++)
			dp[i]=max(dp[i-2]+M[i],dp[i-1]);
		ans+=dp[N];
	}
	printf("%d\n",ans);
	return 0;
}