Language: C++

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

int main() {
  int x;
  cin >> x;

  if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
    cout << A << endl;
  }
  else {
    cout << a << endl;
  }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:12: error: 'A' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |            ^
a.cc:8:19: error: 'B' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                   ^
a.cc:8:25: error: 'C' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                         ^
a.cc:8:31: error: 'D' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                               ^
a.cc:8:37: error: 'E' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                     ^
a.cc:8:43: error: 'F' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                           ^
a.cc:8:49: error: 'G' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                 ^
a.cc:8:55: error: 'H' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                       ^
a.cc:8:61: error: 'I' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                             ^
a.cc:8:67: error: 'J' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                   ^
a.cc:8:73: error: 'K' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                         ^
a.cc:8:79: error: 'L' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                               ^
a.cc:8:85: error: 'N' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                     ^
a.cc:8:91: error: 'M' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                           ^
a.cc:8:97: error: 'O' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                 ^
a.cc:8:103: error: 'P' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                       ^
a.cc:8:109: error: 'Q' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                             ^
a.cc:8:115: error: 'R' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                   ^
a.cc:8:121: error: 'S' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                         ^
a.cc:8:127: error: 'T' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                               ^
a.cc:8:133: error: 'U' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                     ^
a.cc:8:139: error: 'V' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                           ^
a.cc:8:145: error: 'W' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                                 ^
a.cc:8:151: error: 'X' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                                       ^
a.cc:8:157: error: 'Y' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                                             ^
a.cc:8:163: error: 'Z' was not declared in this scope
    8 |   if (x == A|| x==B||x==C||x==D||x==E||x==F||x==G||x==H||x==I||x==J||x==K||x==L||x==N||x==M||x==O||x==P||x==Q||x==R||x==S||x==T||x==U||x==V||x==W||x==X||x==Y||x==Z) {
      |                                                                                                                                                                   ^
a.cc:12:13: error: 'a' was not declared in this scope
   12 |     cout << a << endl;
      |             ^