#include<stdio.h>
#define N 100000
#define YOSHI 2000000000

struct Card{
    char suit;
    int value;
};

struct Card R[N / 2 + 2],L[N / 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 = YOSHI;
    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(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[N],B[N];
    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;
    }
    
    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;
}

