using System;
using System.Collections.Generic;
using System.Linq;
using static System.Math;
using static System.Console;

namespace D_ABC127
{
    class MainClass
    {

        static int[] s;
        static long[] a;

        public static void Main(string[] args)
        {
            s = Array.ConvertAll(ReadLine().Split().ToArray(), int.Parse);
            a = Array.ConvertAll(ReadLine().Split().ToArray(), long.Parse);
            var alist = a.ToList();
        

            var ic = new TupleComparer();
            var pq = new PriorityQueue<Tuple<long,int>>(ic);

            foreach(var item in alist){
                var at = new Tuple<long,int>(item,1);
                pq.Push(at);
            }

            for (int i = 0; i < s[1]; i++)
            {
                long[] bc = Array.ConvertAll(ReadLine().Split().ToArray(), long.Parse);
                var bct = new Tuple<long,int>(bc[1],(int)bc[0]);
                pq.Push(bct);
            }
            
            int n = s[0];
            long ans = 0;
            while(n>0){
                var t = pq.Pop();
                //WriteLine(t.Item1);
                if(t.Item2>=n){
                    ans+=t.Item1 * n;
                    break;
                }else{
                    ans+=t.Item1*t.Item2;
                    n-=t.Item2;
                }
            }
            WriteLine(ans);


        }

        public class TupleComparer :IComparer<Tuple<long,int>>{
            public int Compare(Tuple<long,int> x, Tuple<long,int> y){
                if(x.Item1<y.Item1){
                    return 1;
                }else if(x.Item1>y.Item1){
                    return -1;
                }else{
                    return 0;
                }
            }

        }
        public class PriorityQueue<T> where T : IComparable
        {
            private IComparer<T> _comparer = null;
            private int _type = 0;

            private T[] _heap;
            private int _sz = 0;

            private int _count = 0;

            /// <summary>
            /// Priority Queue with custom comparer
            /// </summary>
            public PriorityQueue(IComparer<T> comparer)
            {
                _heap = new T[128];
                _comparer = comparer;
            }

            /// <summary>
            /// Priority queue
            /// </summary>
            /// <param name="type">0: asc, 1:desc</param>
            public PriorityQueue(int type = 0)
            {
                _heap = new T[128];
                _type = type;
            }

            private int Compare(T x, T y)
            {
                if (_comparer != null) return _comparer.Compare(x, y);
                return _type == 0 ? x.CompareTo(y) : y.CompareTo(x);
            }

            public void Push(T x)
            {
                _count++;
                if (_count > _heap.Length)
                {
                    var newheap = new T[_heap.Length * 2];
                    for (int n = 0; n < _heap.Length; n++) newheap[n] = _heap[n];
                    _heap = newheap;
                }

                //node number
                var i = _sz++;

                while (i > 0)
                {
                    //parent node number
                    var p = (i - 1) / 2;

                    if (Compare(_heap[p], x) <= 0) break;

                    _heap[i] = _heap[p];
                    i = p;
                }

                _heap[i] = x;
            }

            public T Pop()
            {
                _count--;

                T ret = _heap[0];
                T x = _heap[--_sz];

                int i = 0;
                while (i * 2 + 1 < _sz)
                {
                    //children
                    int a = i * 2 + 1;
                    int b = i * 2 + 2;

                    if (b < _sz && Compare(_heap[b], _heap[a]) < 0) a = b;

                    if (Compare(_heap[a], x) >= 0) break;

                    _heap[i] = _heap[a];
                    i = a;
                }

                _heap[i] = x;

                return ret;
            }

            public int Count()
            {
                return _count;
            }

            public T Peek()
            {
                return _heap[0];
            }

            public bool Contains(T x)
            {
                for (int i = 0; i < _sz; i++) if (x.Equals(_heap[i])) return true;
                return false;
            }

            public void Clear()
            {
                while (this.Count() > 0) this.Pop();
            }

            public IEnumerator<T> GetEnumerator()
            {
                var ret = new List<T>();

                while (this.Count() > 0)
                {
                    ret.Add(this.Pop());
                }

                foreach (var r in ret)
                {
                    this.Push(r);
                    yield return r;
                }
            }

            public T[] ToArray()
            {
                T[] array = new T[_sz];
                int i = 0;

                foreach (var r in this)
                {
                    array[i++] = r;
                }

                return array;
            }
        }
    }
}


Measured memory_bytes: 35164