#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;
}
