Language: C++

#include <iostream>

using namespace std;

int main()
{
????????????long int x, y;
	long int n;
	long int d;

	cin >> x >> y;
	n = min(x, y);

	for (d = n; d > 1; d--){
		if (x % d == 0 && y % d == 0) break;
	}
	cout << d << endl;

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:1: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      | ^
a.cc:7:2: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |  ^
a.cc:7:3: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |   ^
a.cc:7:4: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |    ^
a.cc:7:5: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |     ^
a.cc:7:6: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |      ^
a.cc:7:7: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |       ^
a.cc:7:8: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |        ^
a.cc:7:9: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |         ^
a.cc:7:10: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |          ^
a.cc:7:11: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |           ^
a.cc:7:12: error: expected primary-expression before '?' token
    7 | ????????????long int x, y;
      |            ^
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:7:13: error: expected ':' before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
      |             :
a.cc:7:13: error: expected primary-expression before 'long'
    7 | ????????????long int x, y;
      |             ^~~~
a.cc:11:16: error: 'x' was not declared in this scope
   11 |         cin >> x >> y;
      |                ^
a.cc:11:21: error: 'y' was not declared in this scope
   11 |         cin >> x >> y;
      |                     ^