//#define _GLIBCXX_DEBUG

#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++){cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++){for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>vector<vector<T>>vec(ll x, ll y, T w){vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v(ts...))>(a,make_v(ts...));}
template<typename T1, typename T2>ostream &operator<<(ostream &os, const pair<T1, T2>&p){return os << p.first << " " << p.second;}
template<typename T>ostream &operator<<(ostream &os, const vector<T> &v){for(auto &z:v)os << z << " ";cout<<"|"; return os;}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll n,m;cin>>n>>m;
  vector<ll>w(n);
  rep(i,0,n)cin>>w[i];
  ll mxw=*max_element(ALL(w));
  vector<P>p(m);
  rep(i,0,m){
    cin>>p[i].se>>p[i].fi;
    if(p[i].fi<mxw){
      cout<<-1<<endl;
      return 0;
    }
  }
  //荷重、長さ
  //p.EB(INF,INF);
  p.EB(0,0);
  sort(ALL(p));
  rep(i,0,(ll)p.size()-1){
    chmax(p[i+1].se,p[i].se);
  }
  //debug(p,p.size());
  vector<ll>v(n);
  iota(ALL(v),0);
  res=INF;
  do{
    vector<ll>pos(n);
    rep(i,1,n){
      ll nw=w[v[i]];
      ll mx=0;
      rrep(j,0,i){
        nw+=w[v[j]];
        P q=*(--lower_bound(ALL(p),MP(nw,0LL)));
        chmax(mx,q.se-(pos[i-1]-pos[j]));
      }
      pos[i]=pos[i-1]+mx;
    }
    /*if(is_sorted(ALL(v))){
      debug(v,3);debug(pos,3);cout<<endl;
    }*/
    chmin(res,pos[n-1]);
  }while(next_permutation(ALL(v)));
  cout<<res<<endl;
  return 0;
}
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
int n, m, c[10], dl[10], vis[10], ans = 0x3f3f3f3f, lx[10], db[10];
struct judge {
    int l;
    int v;
};
judge a[100010];
bool tmp(judge x, judge y)
{
    if (x.l != y.l) return x.l < y.l;
    else return x.v > y.v;
}
int findl(int x)
{
    int b, e, t;
    b = 1, e = m, t = b + e >> 1;
    while (b < e)
    {
        if (a[t].v < x) b = t;
        else e = t - 1;
        t = b + e +1>> 1;
    }
    if (a[b].v >= x) return 0;
    return a[b].l;
}
void fact()
{
    memset(lx, 0, sizeof lx);
    for (int i = 1; i <= n; i++)
    {
        db[i] = db[i - 1] + c[dl[i]];
    }
    for (int i = 2; i <= n; i++)
        for (int j = 1; j < i; j++)
        {
            int l = findl(db[i] - db[j - 1]);
            lx[i] = max(lx[i], lx[j] + l);
        }
    ans = min(ans, lx[n]);
}
void dfs(int i)
{
    if (i == n + 1)
    {
        fact();
        return;
    }
    for (int j = 1; j <= n; j++)
    {
        if (!vis[j])
        {
            vis[j] = 1;
            dl[i] = j;
            dfs(i + 1);
            vis[j] = 0;
        }
    }
}
int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; i++)  cin >> c[i];
    for (int i = 1; i <= m; i++)  cin >> a[i].l >> a[i].v;
    sort(a + 1, a + m + 1, tmp);
    for (int i = m - 1; i > 0; i--) a[i].v = min(a[i].v, a[i + 1].v);
    for (int i = 1; i <= n; i++) if (c[i] > a[1].v) { cout << -1; return 0; }
    dfs(1);
    cout << ans;
}
