#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 5, mod = 1e9 + 7;
const double pi = acos(-1);
int main() {
  char c;
  cin >> c;
  if (c - 'A' >= 0 && c - 'A' <= 26)
    cout << "A" << endl;
  else
    cout << "a" << endl;
  return 0;
}
