import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;

public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		ContestScanner scan = new ContestScanner();

		final int n = scan.nextInt();
		final Card[] C = new Card[n];

		for(int i=0; i < n; i++)
		{
			C[i] = new Card(scan.next().charAt(0), scan.nextInt());
		}

		(new Solve(n, C)).solve();
	}
}
class Pair<F,S> {
	public final F fst;
	public final S snd;

	public Pair(F f, S s)
	{
		fst = f;
		snd = s;
	}

	public static <F,S> Pair<F,S> of(F f, S s)
	{
		return new Pair<F,S>(f,s);
	}
}
class Card {
	public final char c;
	public final int v;

	public Card(final char c, final int v)
	{
		this.c = c;
		this.v = v;
	}

	public String toString()
	{
		return Character.toString(c) + " " + v;
	}
}
class Solve {
	private int n;
	private Card[] C;

	public Solve(final int n, final Card[] C)
	{
		this.n = n;
		this.C = C;
	}

	public void solve()
	{
		Card[] C = this.C.clone();

		HashMap<Integer, Integer> orderMap = new HashMap<>();

		for(int i=0; i < n; i++)
		{
			if(orderMap.containsKey(C[i].v))
			{
				orderMap.put(C[i].v, (orderMap.get(C[i].v) << 7 | C[i].c));
			}
			else
			{
				orderMap.put(C[i].v, (int)C[i].c);
			}
		}

		quickSort(C, 0, n - 1);

		int v = C[0].v;
		int hash = C[0].c;

		boolean stable = true;

		for(int i=1; i < n + 1; i++)
		{
			if(i == n)
			{
				if(hash != orderMap.get(C[n-1].v)) stable = false;
			}
			else if(C[i].v != v)
			{
				if(hash != orderMap.get(v))
				{
					stable = false;
					break;
				}
				else
				{
					v = C[i].v;
					hash = C[i].c;
				}
			}
			else
			{
				hash = (hash << 7 | C[i].c);
			}
		}

		if(stable) System.out.println("Stable");
		else System.out.println("Not stable");

		StringBuilder sb = new StringBuilder();

		for(int i=0; i < n; i++)
		{
			sb.append(C[i].toString() + "\n");
		}

		System.out.print(sb.toString());
	}

	public void quickSort(Card[] C, final int p, final int r)
	{
		if(p < r)
		{
			int q = partition(C, p, r);

			quickSort(C, p, q - 1);
			quickSort(C, q + 1, r);
		}
	}

	public int partition(Card[] C, int p, final int r)
	{
		int x = C[r].v;
		int i = p - 1;

		for(int j=p; j < r; j++)
		{
			if(C[j].v <= x)
			{
				++i;
				Card tmp = C[j];
				C[j] = C[i];
				C[i] = tmp;
			}
		}
		Card tmp = C[r];
		C[r] = C[i + 1];
		C[i + 1] = tmp;

		return i + 1;
	}
}
class ContestScanner {
	BufferedReader reader;
	String[] line;
	int index;
	public ContestScanner() {
		reader = new BufferedReader(new InputStreamReader(System.in));
	}

	public ContestScanner(String filename) throws FileNotFoundException {
		reader = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));
	}

	public static interface ICreator<T> {
		public T createFromToken(final ContestScanner scanner) throws IOException;
	}

	public static interface IArrayInitializer {
		public void initialize(final ContestScanner scanner, final int i) throws IOException;
	}

	public static interface IObjectInitializer<T> {
		public T initialValue(final ContestScanner scanner);
	}

	public static class ObjectArrayInitializer<T> implements IArrayInitializer {
		protected T[] arr;
		protected final IObjectInitializer<T> initializer;

		private ObjectArrayInitializer(T[] arr, final IObjectInitializer<T> initializer)
		{
			this.arr = arr;
			this.initializer = initializer;
		}

		public static <T> ObjectArrayInitializer<T> create(T[] arr, final IObjectInitializer<T> initializer)
		{
			return new ObjectArrayInitializer<T>(arr, initializer);
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = initializer.initialValue(scanner);
		}

		public T[] getArray()
		{
			return this.arr;
		}
	}


	public static class ByteArrayInitializer implements IArrayInitializer {
		protected byte[] arr;

		private ByteArrayInitializer(final int n)
		{
			this.arr = new byte[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextByte();
		}

		public byte[] getArray()
		{
			return this.arr;
		}
	}

	public static class ShortArrayInitializer implements IArrayInitializer {
		protected short[] arr;

		private ShortArrayInitializer(final int n)
		{
			this.arr = new short[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextShort();
		}

		public short[] getArray()
		{
			return this.arr;
		}
	}

	public static class IntArrayInitializer implements IArrayInitializer {
		protected int[] arr;

		private IntArrayInitializer(final int n)
		{
			this.arr = new int[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextInt();
		}

		public int[] getArray()
		{
			return this.arr;
		}
	}

	public static class LongArrayInitializer implements IArrayInitializer {
		protected long[] arr;

		private LongArrayInitializer(final int n)
		{
			this.arr = new long[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextLong();
		}

		public long[] getArray()
		{
			return this.arr;
		}
	}

	public static class FloatArrayInitializer implements IArrayInitializer {
		protected float[] arr;

		private FloatArrayInitializer(final int n)
		{
			this.arr = new float[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextFloat();
		}

		public float[] getArray()
		{
			return this.arr;
		}
	}

	public static class DoubleArrayInitializer implements IArrayInitializer {
		protected double[] arr;

		private DoubleArrayInitializer(final int n)
		{
			this.arr = new double[n];
		}

		public void initialize(final ContestScanner scanner, final int i) throws IOException {
			this.arr[i] = scanner.nextDouble();
		}

		public double[] getArray()
		{
			return this.arr;
		}
	}

	public String nextToken() throws IOException {
		if(line == null || index >= line.length)
		{
			line = reader.readLine().trim().split(" ");
			index = 0;
		}

		return line[index++];
	}

	public String next() throws IOException {
		return nextToken();
	}

	public String readLine() throws IOException {
		line = null;
		index = 0;

		return reader.readLine();
	}

	public byte nextByte() throws IOException, NumberFormatException {
		return Byte.parseByte(nextToken());
	}

	public short nextShort() throws IOException, NumberFormatException {
		return Short.parseShort(nextToken());
	}

	public int nextInt() throws IOException, NumberFormatException {
		return Integer.parseInt(nextToken());
	}

	public long nextLong() throws IOException, NumberFormatException {
		return Long.parseLong(nextToken());
	}

	public float nextFloat() throws IOException, NumberFormatException {
		return Float.parseFloat(nextToken());
	}

	public double nextDouble() throws IOException, NumberFormatException {
		return Double.parseDouble(nextToken());
	}

	public <T> T nextObject(final ICreator<T> creator) throws IOException, NumberFormatException {
		return creator.createFromToken(this);
	}

	public int[] nextIntArray(final int N) throws IOException, NumberFormatException {
		int[] result = new int[N];

		for(int i=0; i < N; i++) result[i] = nextInt();

		return result;
	}

	public long[] nextLongArray(final int N) throws IOException, NumberFormatException {
		long[] result = new long[N];

		for(int i=0; i < N; i++) result[i] = nextLong();

		return result;
	}

	public float[] nexFloatArray(final int N) throws IOException, NumberFormatException {
		float[] result = new float[N];

		for(int i=0; i < N; i++) result[i] = nextFloat();

		return result;
	}

	public double[] nexDoubleArray(final int N) throws IOException, NumberFormatException {
		double[] result = new double[N];

		for(int i=0; i < N; i++) result[i] = nextDouble();

		return result;
	}

	public <T> T[] nextObjectArray(T[] result, final ICreator<T> creator) throws IOException, NumberFormatException {
		for(int i=0, N=result.length; i < N; i++) result[i] = nextObject(creator);

		return result;
	}

	public <T> ArrayList<T> nextGenericObjectArrayList(final int N, final ICreator<T> creator) throws IOException, NumberFormatException {
		ArrayList<T> result = new ArrayList<T>();
		for(int i=0; i < N; i++) result.add(nextObject(creator));

		return result;
	}

	public void nextTable(final int N, IArrayInitializer... arrayInitializers) throws IOException, NumberFormatException {
		for(int i=0; i < N; i++) for(IArrayInitializer initializer: arrayInitializers)
		{
			initializer.initialize(this, i);
		}
	}
}

Measured memory_bytes: 70808