// Slower C++ solution:
#include<iostream>

#include<utility>

using namespace std;

#define INF 1999999999



pair<char, int> P[1000005];

pair<char, int> S[1000005], L[500005], R[500005];

long long sum=0;



void merge(int left, int mid, int right) {

    int n1 = mid - left;

    int n2 = right - mid;

    for (int i=0; i<n1; i++) {

        L[i] = S[left + i];

    }

    for (int i=0; i<n2; i++) {

        R[i] = S[mid + i];

    }

    L[n1].second = INF;

    R[n2].second = INF;

    int i = 0, j = 0;

    for (int k=left; k<right; k++) {

        if (L[i].second <= R[j].second) {

            S[k] = L[i];

            i++;

        }

        else {

            S[k] = R[j];

            j++;

        }

        sum++;

    }

}



void mergeSort(int left, int right) {

    if (left + 1 < right) {

        int mid = (left + right) / 2;

        mergeSort(left, mid);

        mergeSort(mid, right);

        merge(left, mid, right);

    }

    return;

}



int partition(int p, int r) {

    int x, i, j;

    pair<char, int> t;

    x = P[r].second;

    i = p - 1;

    for (j = p; j < r; j++) {

        if (P[j].second <= x) {

            i++;

            t = P[i]; P[i] = P[j]; P[j] = t;

        }

    }

    t = P[i + 1]; P[i + 1] = P[r]; P[r] = t;

    return i + 1;

}



void quickSort(int p, int r) {

    if (p < r) {

        int q = partition(p, r);

        quickSort(p, q - 1);

        quickSort(q + 1, r);

    }

}



int main() {

    int n;

    cin >> n;

    for (int i=0; i<n; i++) {

        cin >> P[i].first >> P[i].second;

        S[i].first = P[i].first;

        S[i].second = P[i].second;

    }

    quickSort(0, n-1);

    mergeSort(0, n);

    for (int i=0; i<n; i++) {

        if (P[i].first != S[i].first) {

            cout << "Not stable\n";

            break;

        }

        if (i == n - 1) cout << "Stable\n";

    }

    for (int i=0; i<n; i++) {

        cout << P[i].first << " " << P[i].second << endl;

    }

    return 0;

}


// Faster C++ solution for the same problem (measured speedup: 4.3031683512146275x):
/*

#include<iostream>

#include<utility>

using namespace std;

#define INF 1999999999



pair<char, int> P[1000005];

pair<char, int> S[1000005], L[500005], R[500005];

long long sum=0;



void merge(int left, int mid, int right) {

    int n1 = mid - left;

    int n2 = right - mid;

    for (int i=0; i<n1; i++) {

        L[i] = S[left + i];

    }

    for (int i=0; i<n2; i++) {

        R[i] = S[mid + i];

    }

    L[n1].second = INF;

    R[n2].second = INF;

    int i = 0, j = 0;

    for (int k=left; k<right; k++) {

        if (L[i].second <= R[j].second) {

            S[k] = L[i];

            i++;

        }

        else {

            S[k] = R[j];

            j++;

        }

        sum++;

    }

}



void mergeSort(int left, int right) {

    if (left + 1 < right) {

        int mid = (left + right) / 2;

        mergeSort(left, mid);

        mergeSort(mid, right);

        merge(left, mid, right);

    }

    return;

}



int partition(int p, int r) {

    int x, i, j;

    pair<char, int> t;

    x = P[r].second;

    i = p - 1;

    for (j = p; j < r; j++) {

        if (P[j].second <= x) {

            i++;

            t = P[i]; P[i] = P[j]; P[j] = t;

        }

    }

    t = P[i + 1]; P[i + 1] = P[r]; P[r] = t;

    return i + 1;

}



void quickSort(int p, int r) {

    if (p < r) {

        int q = partition(p, r);

        quickSort(p, q - 1);

        quickSort(q + 1, r);

    }

}



int main() {

    int n;

    cin >> n;

    for (int i=0; i<n; i++) {

        cin >> P[i].first >> P[i].second;

        S[i].first = P[i].first;

        S[i].second = P[i].second;

    }

    quickSort(0, n-1);

    mergeSort(0, n);

    for (int i=0; i<n; i++) {

        if (P[i].first != S[i].first) {

            cout << "Not stable\n";

            break;

        }

        if (i == n - 1) cout << "Stable\n";

    }

    for (int i=0; i<n; i++) {

        cout << P[i].first << " " << P[i].second << endl;

    }

    return 0;

}

*/



#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++) {

        // マージソートとクイックソートの結果を比べる

        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;

}