#include<bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef long double ld;
template <typename T> bool chkmin(T &x,T y){return x>y?x=y,1:0;}
template <typename T> bool chkmax(T &x,T y){return x<y?x=y,1:0;}
ll readint(){
ll x=0,f=1; char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int n,m;
int c[10005],a[505],b[505];
int dpa[20005],dpb[20005];
int main(){
n=readint(); m=readint();
for(int i=1;i<=n;i++) c[i]=readint();
for(int i=1;i<=m;i++) a[i]=readint(),b[i]=readint();
for(int i=1;i<=n;i++){
for(int j=n;j>=0;j--) chkmax(dpa[j+1],dpa[j]+c[i]);
}
for(int i=0;i<=20000;i++) dpb[i]=1e9;
dpb[0]=0;
for(int i=1;i<=m;i++){
for(int j=20000-a[i];j>=0;j--) chkmin(dpb[j+a[i]],dpb[j]+b[i]);
}
int ans=0,mx=0;
for(int i=0;i<=20000;i++){
chkmax(mx,dpa[i]);
chkmax(ans,mx-dpb[i]);
}
printf("%d\n",ans);
return 0;
}
