#include <bits/stdc++.h>
using namespace std;
const int mod = 1000000007;
struct mint {
  long long x;
  mint(long long x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(long long t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint& operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream& operator>>(istream& is, const mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
} c(200005);
vector<pair<long long, long long> > prime_factorize(long long N) {
  vector<pair<long long, long long> > res;
  for (long long a = 2; a * a <= N; ++a) {
    if (N % a != 0) continue;
    long long ex = 0;
    while (N % a == 0) {
      ++ex;
      N /= a;
    }
    res.push_back({a, ex});
  }
  if (N != 1) res.push_back({N, 1});
  return res;
}
vector<long long> enum_divisors(long long N) {
  vector<long long> res;
  for (long long i = 1; i * i <= N; ++i) {
    if (N % i == 0) {
      res.push_back(i);
      if (N / i != i) res.push_back(N / i);
    }
  }
  sort(res.begin(), res.end());
  return res;
}
int main(int argc, const char* argv[]) {
  char s;
  cin >> s;
  if (isupper(s)) {
    cout << 'A' << endl;
  } else {
    cout << 'a' << endl;
  }
  return 0;
}
