#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;
}
