#include<bits/stdc++.h>
#define rep(x,y,z) for(int x=y;x<=z;x++)
#define drep(x,y,z) for(int x=y;x>=z;x--)
#define ull unsigned long long
#define ll long long
using namespace std;
inline int read()
{
	int x=0;bool flag=1;char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-')flag=0;ch=getchar();}
	while(ch>='0'&&ch<='9') {x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
	if(flag) return x;
	return ~(x-1);
} 
inline void write(int x)
{
	if(x<0) {x=~(x-1);putchar('-');}
	if(x>9) write(x/10);
	putchar(x%10+'0');
}
////////////////////////
const int N=270;
int nc,bc;
int n[N];
int f[N],a[N][2];//0深度，1长度 
int ans;
int main()
{
    freopen("snowboots_silver_18feb.in","r",stdin);
	freopen("snowboots_silver_18feb.out","w",stdout);
    nc=read(),bc=read();
    rep(i,1,nc) n[i]=read();
    rep(i,1,bc) a[i][0]=read(),a[i][1]=read();
    f[1]=1;
    int s1,s2;
    rep(i,1,bc)
    {
        s1=0;
        s2=1;
        rep(o,2,nc)
        {  
           if(!f[o]&&s2&&a[i][0]>=n[o]) f[o]=i;
           if(o-a[i][1]>=1)
           {
               if(f[o-a[i][1]]&&a[i][0]>=n[o-a[i][1]]) s2--;
           }
           if(f[o]&&a[i][0]>=n[o]) s2++;   
        }
        if(f[nc]) break;    
    }
//    cout<<"f:\n";
//    for(int i=1;i<=nc;i++) cout<<f[i]<<" ";
//    cout<<endl;
    cout<<f[nc]-1<<endl;
    return 0;
}