#include<stdio.h>
#define MAX 100000
#define SENTINEL 2000000000


struct Card{
	char suit;
	int value;
};

struct Card L[MAX / 2 + 2], R[MAX / 2 + 2];

void merge(struct Card A[], int n, int left, int mid, int right){
	int i,j,k;
	int n1 = mid - left;
	int n2 = right - mid;
	for( i=0; i<n1; i++) L[i] = A[left + i];
	for( i=0; i<n2; i++) R[i] = A[mid + i];
	L[n1].value = R[n2].value = SENTINEL;
	i = j = 0;
	
	for( k=left; k<right; k++){
		if(L[i].value <= R[j].value){
			A[k] = L[i++];
		} else{
			A[k] = R[j++];
		}
	}
}

void mergeSort(struct Card A[], int n, int left, int right){
	int mid;
	if( left + 1 < right){
		mid = (left+right) / 2;
		mergeSort(A, n, left, mid);
		mergeSort(A, n, mid, right);
		merge(A, n, left, mid, right);
	}
}

int partition(struct Card A[], int n, int p, int r){
	int i, j;
	struct Card t, x;
	x = A[r];
	i = p - 1;
	for( j=p; j<r; j++){
		if( A[j].value <= x.value ){
			i++;
			t = A[i]; A[i] = A[j]; A[j]=t;
		}
	}
	t=A[i+1]; A[i+1]=A[r]; A[r]=t;
	return i+1;
}

void quickSort( struct Card A[], int n, int p, int r){
	int q;
	if( p<r ){
		q=partition(A, n, p, r);
		quickSort(A,n,p,q-1);
		quickSort(A,n,q+1,r);
	}
}

int main(){
	int n, i, v;
	struct Card A[MAX], B[MAX];
	char S[10];
	int stable=1;
	
	scanf("%d",&n);
	
	for(i=0; i<n; i++){
		scanf("%s %d",S, &v);
		A[i].suit = B[i].suit = S[0];
		A[i].value = B[i].value = v;
	}
	
	mergeSort(A, n, 0, n);
	quickSort(B, n, 0, n-1);
	
	for( i=0; i<n; i++){
		//マージソートとクイックソートの結果を比べる
		if (A[i].suit != B[i].suit) stable =0;
	}
	
	if( stable == 1 ) printf("Stable\n");
	else printf("Not stable\n");
	for( i=0; i<n; i++){
		printf("%c %d\n", B[i].suit, B[i].value);
	}
	
	return 0;
}
