#include <stdio.h>
#define MAX 100000

typedef struct{
    char suit;
    int value;
}Card;

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

void merge(Card*,int,int,int,int);
void mergeSort(Card*,int,int,int);
int partition(Card*,int,int,int);
void quickSort(Card*,int,int,int);

int main(){
    int n,i,value;
    Card A[MAX],B[MAX];
    char suit;

    scanf("%d",&n);

    for(i=0;i<n;i++){
        scanf(" %c%d",&suit,&value);
        
        A[i].suit=suit;
        B[i].suit=suit;
        A[i].value=value;
        B[i].value=value;
    }

    mergeSort(A,n,0,n);
    quickSort(B,n,0,n-1);

    for(i=0;i<n;i++){
        if(A[i].suit!=B[i].suit){
            printf("Not stable\n");
            break;
        }
        if(i==n-1) printf("Stable\n");
    }

    for(i=0;i<n;i++){
        printf("%c %d\n",B[i].suit,B[i].value);
    }

    return 0;
}

void merge(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=1000000001;
    R[n2].value=1000000001;
        
    i=0;
    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(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(Card *A,int n,int p,int r){
    int i,j;
    Card tmp,x;

    x=A[r];
    i=p-1;

    for(j=p;j<r;j++){
        if(A[j].value<=x.value){
            i++;
            tmp=A[i];
            A[i]=A[j];
            A[j]=tmp;
        }
    }

    tmp=A[i+1];
    A[i+1]=A[r];
    A[r]=tmp;

    return i+1;
}

void quickSort(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);
    }

}
