import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Random;
import java.util.StringTokenizer;
public class C {
    static void shuffle(int[] a)
    {
        int n=a.length;
        Random rnd = new Random(System.nanoTime());
        for (int i=0; i<n; ++i)
        {
            int v=rnd.nextInt(n-i);
            int tmp=a[i+v];
            a[i+v]=a[i];
            a[i]=tmp;
        }
    }
    public static void main(String[] args) throws Exception {
        InputReader in = new InputReader(System.in);
        int n=in.nextInt();
        int q=in.nextInt();
        int a[]= new int [n];
        int b[]=new int[n];
        for (int i=0; i<n; ++i)
            a[i]=in.nextInt();
        for (int i=0; i<q; ++i)
        {
            int l=in.nextInt();
            int r=in.nextInt();
            l--;
            r--;
            b[l]++;
            if (r<n-1)
                b[r+1]--;
        }
        int v=0;
        shuffle(a);
        Arrays.sort(a);
        int val[] = new int[n];
        for (int i=0; i<n; ++i)
        {
            v+=b[i];
            val[i]=v;
        }
        shuffle(val);
        Arrays.sort(val);
        long res=0;
        for (int i=0; i<n; ++i)
        {
            long c=a[i];
            c*=val[i];
            res+=c;
        }
        System.out.println(res);
    }
}


class InputReader {
    BufferedReader reader;
    StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream));
        tokenizer = null;
    }

    public String next() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public long nextLong() {
        return Long.parseLong(next());
    }
    public int nextInt() {
        return Integer.parseInt(next());
    }

}