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 << "xは10より小さい" << endl;
  }
  else {
    cout << "xは10より小さくない" << 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:8:18: 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:8:23: 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:8:28: 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:8:33: 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:8:38: 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:8:43: 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:8:48: 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:8:53: 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:8:58: 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:8:63: 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:8:68: 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:8:73: 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:8:78: 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:8:83: 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:8:88: 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:8:93: 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:8:98: 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:8:103: 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:8:108: 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:8:113: 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:8:118: 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:8:123: 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:8:128: 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:8:133: 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:8:138: 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) {
      |                                                                                                                                          ^