View Compilation Error

0_0_35131487_25668.cpp: In function 'll gcd(ll, ll)':
0_0_35131487_25668.cpp:13:31: error: expected ';' before 'gcd'
 ll gcd(ll a, ll b) { return b gcd(b, a % b) : a; }
                               ^
0_0_35131487_25668.cpp:13:45: error: expected ';' before ':' token
 ll gcd(ll a, ll b) { return b gcd(b, a % b) : a; }
                                             ^