#include <stdio.h>
#define MAX 100000
#define SEN 20000000000

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;
	int n1 = mid;
	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=SEN;

	
	int i=0,j=0,k;
	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 p ,int r){
	int i,j;
	struct Card x,t;
	x=A[r];
	i=p-1;
	
	for(j=p;j<r;j++){
		if(A[j].value<=x.value){
			i++;
		t=A[j];A[j]=A[i];A[i]=t;
	
		}
	}
	t=A[r];A[r]=A[i+1];A[i+1]=t;
	return i+1;
}


void quickSort(struct Card A[], int n,int p,int r){
	int q;
	if(p<r){
		q = partition(A,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++){
		if(A[i].suit!=B[i].suit){
		stable=0;
		break;}
	}
	
	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;
}