View Compilation Error

0_0_38245768_12094.cpp: In function 'int gcd(int, int)':
0_0_38245768_12094.cpp:6:10: error: expected primary-expression at end of input
  return b?
          ^
0_0_38245768_12094.cpp:6:10: error: expected ':' at end of input
0_0_38245768_12094.cpp:6:10: error: expected primary-expression at end of input
0_0_38245768_12094.cpp:6:10: error: expected ';' at end of input
0_0_38245768_12094.cpp:6:10: error: expected '}' at end of input