'use strict';

function Main(input) {
    const tmp = input.trim().split('\n')[0];

    const reg = /[A-Z]/;

    if (tmp.match(reg)) {
        console.log('A');
    } else {
        console.log('a');
    }

    return;
}
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));