#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];
    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(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[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; 
    }

    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;
}
