/in/foo.cc: In function 'int main()':
/in/foo.cc:24:46: error: 'gcd' was not declared in this scope
 if(__gcd( a[i], t1) == 1 && gcd(t3 / a[i], t2) == 1)
                                              ^
/in/foo.cc:26:21: error: 'gcd' was not declared in this scope
 if(gcd(t3 / a[i], t1) == 1 && __gcd( a[i], t2) == 1)
                     ^