Language: C++

#include<iostream>
#include<cstdio>
??
int a;
int main(){
????int i = 1;
????while(1){
??
????????scanf("%d",&a);
????????if(a == 0)
????????break;
????????printf("Case %d: %d\n",i++,a);
????}
????return 0;
}

Compiler output:
a.cc:3:1: error: expected unqualified-id before '?' token
    3 | ??
      | ^
a.cc: In function 'int main()':
a.cc:6:1: error: expected primary-expression before '?' token
    6 | ????int i = 1;
      | ^
a.cc:6:2: error: expected primary-expression before '?' token
    6 | ????int i = 1;
      |  ^
a.cc:6:3: error: expected primary-expression before '?' token
    6 | ????int i = 1;
      |   ^
a.cc:6:4: error: expected primary-expression before '?' token
    6 | ????int i = 1;
      |    ^
a.cc:6:5: error: expected primary-expression before 'int'
    6 | ????int i = 1;
      |     ^~~
a.cc:6:5: error: expected ':' before 'int'
    6 | ????int i = 1;
      |     ^~~
      |     :
a.cc:6:5: error: expected primary-expression before 'int'
    6 | ????int i = 1;
      |     ^~~
a.cc:6:5: error: expected ':' before 'int'
    6 | ????int i = 1;
      |     ^~~
      |     :
a.cc:6:5: error: expected primary-expression before 'int'
    6 | ????int i = 1;
      |     ^~~
a.cc:6:5: error: expected ':' before 'int'
    6 | ????int i = 1;
      |     ^~~
      |     :
a.cc:6:5: error: expected primary-expression before 'int'
    6 | ????int i = 1;
      |     ^~~
a.cc:6:5: error: expected ':' before 'int'
    6 | ????int i = 1;
      |     ^~~
      |     :
a.cc:6:5: error: expected primary-expression before 'int'
    6 | ????int i = 1;
      |     ^~~
a.cc:7:1: error: expected primary-expression before '?' token
    7 | ????while(1){
      | ^
a.cc:7:2: error: expected primary-expression before '?' token
    7 | ????while(1){
      |  ^
a.cc:7:3: error: expected primary-expression before '?' token
    7 | ????while(1){
      |   ^
a.cc:7:4: error: expected primary-expression before '?' token
    7 | ????while(1){
      |    ^
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1){
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1){
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1){
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1){
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1){
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1){
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1){
      |     ^~~~~
a.cc:7:5: error: expected ':' before 'while'
    7 | ????while(1){
      |     ^~~~~
      |     :
a.cc:7:5: error: expected primary-expression before 'while'
    7 | ????while(1){
      |     ^~~~~
a.cc:14:1: error: expected primary-expression before '?' token
   14 | ????return 0;
      | ^
a.cc:14:2: error: expected primary-expression before '?' token
   14 | ????return 0;
      |  ^
a.cc:14:3: error: expected primary-expression before '?' token
   14 | ????return 0;
      |   ^
a.cc:14:4: error: expected primary-expression before '?' token
   14 | ????return 0;
      |    ^
a.cc:14:5: error: expected primary-expression before 'return'
   14 | ????return 0;
      |     ^~~~~~
a.cc:14:5: error: expected ':' before 'return'
   14 | ????return 0;
      |     ^~~~~~
      |     :
a.cc:14:5: error: expected primary-expression before 'return'
   14 | ????return 0;
      |     ^~~~~~
a.cc:14:5: error: expected ':' before 'return'
   14 | ????return 0;
      |     ^~~~~~
      |     :
a.cc:14:5: error: expected primary-expression before 'return'
   14 | ????return 0;
      |     ^~~~~~
a.cc:14:5: error: expected ':' before 'return'
   14 | ????return 0;
      |     ^~~~~~
      |     :
a.cc:14:5: error: expected primary-expression before 'return'
   14 | ????return 0;
      |     ^~~~~~
a.cc:14:5: error: expected ':' before 'return'
   14 | ????return 0;
      |     ^~~~~~
      |     :
a.cc:14:5: error: expected primary-expression before 'return'
   14 | ????return 0;
      |     ^~~~~~