#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) {
	if(left+1 < right) {
		int 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;
}
