#include<stdio.h>

#define MAX 100000
#define SENTINEL 2000000000

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

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

void merge(Card A[], int n, int left, int mid, int right)
{
    int i,k,j;
    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(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 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(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 i,n,v;
    Card A[MAX];
    Card 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;
    }

    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;
}

