import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.NoSuchElementException;

public class Main {

	public static void main(String[] args) {
		IO sc = new IO();
		int n = sc.nextInt();
		int k = sc.nextInt();
		int[] c = new int[n];
		int[] g = new int[n];
		sc.arrayInt(c,g);
		ArrayList<ArrayList<Integer>> group = new ArrayList<ArrayList<Integer>>(n);
		for(int i=0;i<10;i++) {
			group.add(new ArrayList<Integer>());
		}
		for(int i=0;i<n;i++) {
			group.get(g[i]-1).add(c[i]);
		}
		for(int i=0;i<10;i++) {
			ArrayList<Integer> al = group.get(i);
			Collections.sort(al,Collections.reverseOrder());
			al.add(0,0);
			for(int j=1;j<al.size();j++) {
				al.set(j, al.get(j-1) + al.get(j));
			}
			for(int j=1;j<al.size();j++) {
				al.set(j, al.get(j) + j * (j-1));
			}
		}
		int[][] dp = new int[11][k+1];
		for(int i=1;i<=10;i++) {
			for(int j=1;j<=k;j++) {
				for(int l=0;l<=j;l++) {
					if (l >= group.get(i-1).size()) {
						break;
					}
					dp[i][j] = Math.max(dp[i][j], dp[i-1][j-l] + group.get(i-1).get(l));
				}
			}
		}
		System.out.println(dp[10][k]);
	}

}
class IO {
	private final InputStream in;
	private final PrintWriter out = new PrintWriter(System.out);
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;

	public IO() { this(System.in);}
	public IO(InputStream source) { this.in = source;}
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	private static boolean isNewLine(int c) { return c == '\n' || c == '\r';}
	private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
	private void skipNewLine() { while(hasNextByte() && isNewLine(buffer[ptr])) ptr++;}
	public boolean hasNext() { skipUnprintable(); return hasNextByte();}
	public boolean hasNextLine() { skipNewLine(); return hasNextByte();}
	public String next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public String nextLine() {
		if (!hasNextLine()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(!isNewLine(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else{
				return minus ? -n : n;
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
			throw new NumberFormatException();
		}
		return (int) nl;
	}
	public char nextChar() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		return (char) readByte();
	}
	public double nextDouble() { return Double.parseDouble(next());}
	public int[] arrayInt(int n) { int[] a = new int[n]; for(int i=0;i<n;i++) a[i] = nextInt(); return a;};
	public long[] arrayLong(int n) { long[] a = new long[n]; for(int i=0;i<n;i++) a[i] = nextLong(); return a;};
	public double[] arrayDouble(int n) { double[] a = new double[n]; for(int i=0;i<n;i++) a[i] = nextDouble(); return a;};
	public void arrayInt(int[]... a) {
		for(int i=0;i<a[0].length;i++) {
			for(int j=0;j<a.length;j++) {
				a[j][i] = nextInt();
			}
		}
	}
	public void println(long x) { out.println(x);}
	public void println(double x) { out.println(x);}
	public void println(String s) { out.println(s);}
	public void println() { out.println(); }
	public void print(long x) { out.print(x); }
	public void print(double x) { out.print(x); }
	public void print(String s) { out.print(s); }
	public void print(char c) {out.print(c);}
	public void flush() {out.flush(); }
}

Measured memory_bytes: 30052