View Compilation Error

1_868_10078_2376.cpp: In function 'long long int gcd(long long int, long long int)':
1_868_10078_2376.cpp:7:13: error: 'y' was not declared in this scope
      return y?gcd(y,x%y):x;
             ^
1_868_10078_2376.cpp:7:21: error: 'x' was not declared in this scope
      return y?gcd(y,x%y):x;
                     ^