// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;

struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;

#define P(x) cout << (x) << endl

#define p(x) cout << (x)

#define all(c) (c).begin(), (c).end()

#define rall(c) (c).rbegin(), (c).rend()

#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));

#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)

#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)

#define len(x) ((int)(x).size())

#define mp make_pair

#define eb emplace_back

typedef long long ll;

typedef vector<int> vi;

typedef vector<double> vd;

typedef vector<long long> vll;

typedef vector<string> vs;

typedef vector<bool> vb;

constexpr int MAX = 1e6;

int n;

vector<pair<char, int>> L(MAX / 2 + 2), R(MAX / 2 + 2);

inline void merge(vector<pair<char, int>> &a, int left, int mid, int right) {

	int n1 = mid - left;

	int n2 = right - mid;

	rep(i, 0, n1) L[i] = a[left + i];

	rep(i, 0, n2) R[i] = a[mid + i];

	L[n1] = R[n2] = mp('Z', 1e9);

	int i = 0, j = 0;

	rep(k, left, right) {

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

			a[k] = L[i];

			++i;

		} else {

			a[k] = R[j];

			++j;

		}

	}

}

inline void mergeSort(vector<pair<char, int>> &a, int left, int right) {

	if(left + 1 < right) {

		int mid = (left + right) / 2;

		mergeSort(a, left, mid);

		mergeSort(a, mid, right);

		merge(a, left, mid, right);

	}

}

inline int partition(vector<pair<char, int>> &a, int p, int r) {

	int x = a[r].second;

	int i = p - 1;

	rep(j, p, r) {

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

			swap(a[++i], a[j]);

		}

	}

	swap(a[++i], a[r]);

	return i;

}

inline void quickSort(vector<pair<char, int>> &a, int p, int r) {

	if(p < r) {

		int q = partition(a, p, r);

		quickSort(a, p, q - 1);

		quickSort(a, q + 1, r);

	}

}

int main() {

	cin >> n;

	vector<pair<char, int>> v, mv; v.reserve(100001);

	char s;

	int x;

	rep(i, 0, n) {

		cin >> s >> x;

		v.eb(mp(s, x));

	}

	mv.assign(all(v));

	quickSort(v, 0, n - 1);

	mergeSort(mv, 0, n);

	P(v == mv ? "Stable" : "Not stable");

	for(auto i : v) {

		cout << i.first << ' ' << i.second << endl;

	}

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 9.45591049826626x):
#include <bits/stdc++.h>

using namespace std;

struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;

#define P(x) cout << (x) << endl

#define p(x) cout << (x)

#define all(c) (c).begin(), (c).end()

#define rall(c) (c).rbegin(), (c).rend()

#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));

#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)

#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)

#define len(x) ((int)(x).size())

#define mp make_pair

#define eb emplace_back

typedef long long ll;

typedef vector<int> vi;

typedef vector<double> vd;

typedef vector<long long> vll;

typedef vector<string> vs;

typedef vector<bool> vb;

constexpr int MAX = 1e6;

int n;

inline void merge(vector<pair<char, int>> &a, int left, int mid, int right) {

	int n1 = mid - left;

	int n2 = right - mid;

	vector<pair<char, int>> L(n1), R(n2);

	copy(a.begin() + left, a.begin() + mid, L.begin());

	copy(a.begin() + mid, a.begin() + right, R.begin());

	L.eb(mp('Z', 1e9 + 5));

	R.eb(mp('Z', 1e9 + 5));

	int i = 0, j = 0;

	rep(k, left, right) {

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

			a[k] = L[i];

			++i;

		} else {

			a[k] = R[j];

			++j;

		}

	}

}

inline void mergeSort(vector<pair<char, int>> &a, int left, int right) {

	if(left + 1 < right) {

		int mid = (left + right) / 2;

		mergeSort(a, left, mid);

		mergeSort(a, mid, right);

		merge(a, left, mid, right);

	}

}

inline int partition(vector<pair<char, int>> &a, int p, int r) {

	int x = a[r].second;

	int i = p - 1;

	rep(j, p, r) {

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

			swap(a[++i], a[j]);

		}

	}

	swap(a[++i], a[r]);

	return i;

}

inline void quickSort(vector<pair<char, int>> &a, int p, int r) {

	if(p < r) {

		int q = partition(a, p, r);

		quickSort(a, p, q - 1);

		quickSort(a, q + 1, r);

	}

}

int main() {

	cin >> n;

	vector<pair<char, int>> v, mv; v.reserve(100001);

	char s;

	int x;

	rep(i, 0, n) {

		cin >> s >> x;

		v.eb(mp(s, x));

	}

	mv.assign(all(v));

	quickSort(v, 0, n - 1);

	mergeSort(mv, 0, n);

	P(v == mv ? "Stable" : "Not stable");

	rep(i, 0, n) {

		cout << v[i].first << ' ' << v[i].second << endl;

	}

	return 0;

}