#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  char n;
  cin >> n;
  long long int cnt = (int)n;
  if (cnt >= 97)
    cout << "a" << endl;
  else
    cout << "A" << endl;
  return 0;
}
