package contest180223;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Queue;

public class E {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		int n = ni(), K = ni();
		long P = nl();
		if(P == 0){
			out.println((long)n*(n+1)*(n+2)/6);
			return;
		}
		int[][] d = new int[n][n];
		for(int i = 0;i < n;i++){
			Arrays.fill(d[i], 999999999);
		}
		Queue<Integer> q = new ArrayDeque<>();
		for(int i = 0;i < K;i++){
			int r = ni()-1, c = ni()-1;
			d[r][c] = 0;
			q.add(r<<16|c);
		}
		int[] dr = { 1, 1, 0, 0, -1, -1 };
		int[] dc = { 0, 1, 1, -1, -1, 0};
		while(!q.isEmpty()){
			int cur = q.poll();
			int r = cur>>>16, c = cur&65535;
			for(int k = 0;k < 6;k++){
				int nr = r + dr[k], nc = c + dc[k];
				if(nr >= 0 && nr < n && nc >= 0 && nc <= nr && d[nr][nc] > d[r][c] + 1){
					d[nr][nc] = d[r][c] + 1;
					q.add(nr<<16|nc);
				}
			}
		}
		
		int[][] rsum = new int[n+1][n+1];
		for(int i = 0;i < n;i++){
			for(int j = 0;j <= i;j++){
				rsum[i+1][j+1] = rsum[i][j] + d[i][j];
			}
		}
		
		int[][] lsum = new int[n+1][n+1];
		for(int i = 0;i < n;i++){
			for(int j = 0;j <= i;j++){
				lsum[i+1][j+1] = lsum[i][j+1] + d[i][j];
			}
		}
		
		int[][] vsum = new int[n+1][n+1];
		for(int i = 0;i < n;i++){
			for(int j = 0;j <= i;j++){
				vsum[i+1][j+1] = vsum[i+1][j] + d[i][j];
			}
		}
//		tr(d);
//		tr(rsum);
//		tr(lsum);
//		tr(vsum);
		
		ans = 0;
		dfs(0, 0, 0, rsum, lsum, vsum, n, 0L, P);
		out.println(ans);
	}
	
	long ans = 0;
	
	void dfs(int r, int c, int b, int[][] rsum, int[][] lsum, int[][] vsum, int n, long S, long P)
	{
		if(r == n)return;
		while(S < P && b < n){
			S += vsum[b+1][c+b-r+1] - vsum[b+1][c];
			b++;
		}
		if(S < P)return;
		ans += n-b+1;
		dfs(r+1, c, b, rsum, lsum, vsum, n, S - rsum[b-1+1][c+b-1-r+1] + rsum[r][c], P);
		if(r == c){
			dfs(r+1, c+1, b, rsum, lsum, vsum, n, S - lsum[b-1+1][c+1] + lsum[r][c+1], P);
		}
	}
	
	void run() throws Exception
	{
//		int n = 4000, m = 1;
//		Random gen = new Random();
//		StringBuilder sb = new StringBuilder();
//		sb.append(n + " ");
//		sb.append(m + " ");
//		sb.append(0L + " ");
//		for (int i = 0; i < m; i++) {
//			int v1 = gen.nextInt(n);
//			int v2 = gen.nextInt(v1+1);
//			sb.append(v1 + 1 + " ");
//			sb.append(v2 + 1 + " ");
//		}
//		INPUT = sb.toString();

		
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new E().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}