#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];//左半分の数列を挿入
    for(i=0;i<n2;i++)R[i]=A[mid+i];//右半分の数列を挿入
    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){// 要素数が1以上の場合
        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。(マージソートは安定なソート)
        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;
}
