Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  char alpha;
  cin >> alpha;
  if (alpha == a || alpha == b || alpha == c || alpha == d || 
      alpha == e || alpha == f || alpha == g || alpha == h ||
      alpha == i || alpha == j || alpha == k || alpha == l || 
      alpha == m || alpha == n || alpha == o || alpha == p || 
      alpha == q || alpha == r || alpha == s || alpha == t || 
      alpha == u || alpha == v || alpha == w || alpha == x ||
      alpha == y || alpha == z)
    cout << 'a' << endl;
  else if (alpha == A || alpha == B || alpha == C || alpha == D || 
      alpha == E || alpha == F || alpha == G || alpha == H ||
      alpha == I || alpha == J || alpha == K || alpha == L || 
      alpha == M || alpha == N || alpha == O || alpha == P || 
      alpha == Q || alpha == R || alpha == S || alpha == T || 
      alpha == U || alpha == V || alpha == W || alpha == X ||
      alpha == Y || alpha == Z)
    cout << 'A' << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:16: error: 'a' was not declared in this scope
    7 |   if (alpha == a || alpha == b || alpha == c || alpha == d ||
      |                ^
a.cc:7:30: error: 'b' was not declared in this scope
    7 |   if (alpha == a || alpha == b || alpha == c || alpha == d ||
      |                              ^
a.cc:7:44: error: 'c' was not declared in this scope
    7 |   if (alpha == a || alpha == b || alpha == c || alpha == d ||
      |                                            ^
a.cc:7:58: error: 'd' was not declared in this scope
    7 |   if (alpha == a || alpha == b || alpha == c || alpha == d ||
      |                                                          ^
a.cc:8:16: error: 'e' was not declared in this scope
    8 |       alpha == e || alpha == f || alpha == g || alpha == h ||
      |                ^
a.cc:8:30: error: 'f' was not declared in this scope
    8 |       alpha == e || alpha == f || alpha == g || alpha == h ||
      |                              ^
a.cc:8:44: error: 'g' was not declared in this scope
    8 |       alpha == e || alpha == f || alpha == g || alpha == h ||
      |                                            ^
a.cc:8:58: error: 'h' was not declared in this scope
    8 |       alpha == e || alpha == f || alpha == g || alpha == h ||
      |                                                          ^
a.cc:9:16: error: 'i' was not declared in this scope
    9 |       alpha == i || alpha == j || alpha == k || alpha == l ||
      |                ^
a.cc:9:30: error: 'j' was not declared in this scope; did you mean 'jn'?
    9 |       alpha == i || alpha == j || alpha == k || alpha == l ||
      |                              ^
      |                              jn
a.cc:9:44: error: 'k' was not declared in this scope
    9 |       alpha == i || alpha == j || alpha == k || alpha == l ||
      |                                            ^
a.cc:9:58: error: 'l' was not declared in this scope
    9 |       alpha == i || alpha == j || alpha == k || alpha == l ||
      |                                                          ^
a.cc:10:16: error: 'm' was not declared in this scope; did you mean 'tm'?
   10 |       alpha == m || alpha == n || alpha == o || alpha == p ||
      |                ^
      |                tm
a.cc:10:30: error: 'n' was not declared in this scope; did you mean 'yn'?
   10 |       alpha == m || alpha == n || alpha == o || alpha == p ||
      |                              ^
      |                              yn
a.cc:10:44: error: 'o' was not declared in this scope
   10 |       alpha == m || alpha == n || alpha == o || alpha == p ||
      |                                            ^
a.cc:10:58: error: 'p' was not declared in this scope
   10 |       alpha == m || alpha == n || alpha == o || alpha == p ||
      |                                                          ^
a.cc:11:16: error: 'q' was not declared in this scope
   11 |       alpha == q || alpha == r || alpha == s || alpha == t ||
      |                ^
a.cc:11:30: error: 'r' was not declared in this scope
   11 |       alpha == q || alpha == r || alpha == s || alpha == t ||
      |                              ^
a.cc:11:44: error: 's' was not declared in this scope
   11 |       alpha == q || alpha == r || alpha == s || alpha == t ||
      |                                            ^
a.cc:11:58: error: 't' was not declared in this scope; did you mean 'tm'?
   11 |       alpha == q || alpha == r || alpha == s || alpha == t ||
      |                                                          ^
      |                                                          tm
a.cc:12:16: error: 'u' was not declared in this scope
   12 |       alpha == u || alpha == v || alpha == w || alpha == x ||
      |                ^
a.cc:12:30: error: 'v' was not declared in this scope
   12 |       alpha == u || alpha == v || alpha == w || alpha == x ||
      |                              ^
a.cc:12:44: error: 'w' was not declared in this scope
   12 |       alpha == u || alpha == v || alpha == w || alpha == x ||
      |                                            ^
a.cc:12:58: error: 'x' was not declared in this scope
   12 |       alpha == u || alpha == v || alpha == w || alpha == x ||
      |                                                          ^
a.cc:13:16: error: 'y' was not declared in this scope; did you mean 'yn'?
   13 |       alpha == y || alpha == z)
      |                ^
      |                yn
a.cc:13:30: error: 'z' was not declared in this scope
   13 |       alpha == y || alpha == z)
      |                              ^
a.cc:15:21: error: 'A' was not declared in this scope
   15 |   else if (alpha == A || alpha == B || alpha == C || alpha == D ||
      |                     ^
a.cc:15:35: error: 'B' was not declared in this scope
   15 |   else if (alpha == A || alpha == B || alpha == C || alpha == D ||
      |                                   ^
a.cc:15:49: error: 'C' was not declared in this scope
   15 |   else if (alpha == A || alpha == B || alpha == C || alpha == D ||
      |                                                 ^
a.cc:15:63: error: 'D' was not declared in this scope
   15 |   else if (alpha == A || alpha == B || alpha == C || alpha == D ||
      |                                                               ^
a.cc:16:16: error: 'E' was not declared in this scope
   16 |       alpha == E || alpha == F || alpha == G || alpha == H ||
      |                ^
a.cc:16:30: error: 'F' was not declared in this scope
   16 |       alpha == E || alpha == F || alpha == G || alpha == H ||
      |                              ^
a.cc:16:44: error: 'G' was not declared in this scope
   16 |       alpha == E || alpha == F || alpha == G || alpha == H ||
      |                                            ^
a.cc:16:58: error: 'H' was not declared in this scope
   16 |       alpha == E || alpha == F || alpha == G || alpha == H ||
      |                                                          ^
a.cc:17:16: error: 'I' was not declared in this scope
   17 |       alpha == I || alpha == J || alpha == K || alpha == L ||
      |                ^
a.cc:17:30: error: 'J' was not declared in this scope
   17 |       alpha == I || alpha == J || alpha == K || alpha == L ||
      |                              ^
a.cc:17:44: error: 'K' was not declared in this scope
   17 |       alpha == I || alpha == J || alpha == K || alpha == L ||
      |                                            ^
a.cc:17:58: error: 'L' was not declared in this scope
   17 |       alpha == I || alpha == J || alpha == K || alpha == L ||
      |                                                          ^
a.cc:18:16: error: 'M' was not declared in this scope
   18 |       alpha == M || alpha == N || alpha == O || alpha == P ||
      |                ^
a.cc:18:30: error: 'N' was not declared in this scope
   18 |       alpha == M || alpha == N || alpha == O || alpha == P ||
      |                              ^
a.cc:18:44: error: 'O' was not declared in this scope
   18 |       alpha == M || alpha == N || alpha == O || alpha == P ||
      |                                            ^
a.cc:18:58: error: 'P' was not declared in this scope
   18 |       alpha == M || alpha == N || alpha == O || alpha == P ||
      |                                                          ^
a.cc:19:16: error: 'Q' was not declared in this scope
   19 |       alpha == Q || alpha == R || alpha == S || alpha == T ||
      |                ^
a.cc:19:30: error: 'R' was not declared in this scope
   19 |       alpha == Q || alpha == R || alpha == S || alpha == T ||
      |                              ^
a.cc:19:44: error: 'S' was not declared in this scope
   19 |       alpha == Q || alpha == R || alpha == S || alpha == T ||
      |                                            ^
a.cc:19:58: error: 'T' was not declared in this scope
   19 |       alpha == Q || alpha == R || alpha == S || alpha == T ||
      |                                                          ^
a.cc:20:16: error: 'U' was not declared in this scope
   20 |       alpha == U || alpha == V || alpha == W || alpha == X ||
      |                ^
a.cc:20:30: error: 'V' was not declared in this scope
   20 |       alpha == U || alpha == V || alpha == W || alpha == X ||
      |                              ^
a.cc:20:44: error: 'W' was not declared in this scope
   20 |       alpha == U || alpha == V || alpha == W || alpha == X ||
      |                                            ^
a.cc:20:58: error: 'X' was not declared in this scope
   20 |       alpha == U || alpha == V || alpha == W || alpha == X ||
      |                                                          ^
a.cc:21:16: error: 'Y' was not declared in this scope
   21 |       alpha == Y || alpha == Z)
      |                ^
a.cc:21:30: error: 'Z' was not declared in this scope
   21 |       alpha == Y || alpha == Z)
      |                              ^