View Compilation Error

0_0_15333960_1915.cpp: In function 'int main()':
0_0_15333960_1915.cpp:3:89: error: '__gcd' is not a member of 'std'
 int main(){int t,n,a,b;scanf("%d",&t);for(int _=1;_<=t;_++){scanf("%d%d%d",&n,&a,&b);(n/std::__gcd(a,b)-2)&1?printf("Case #%d: Yuwgna\n", _):printf("Case #%d: Iaka\n", _);}}
                                                                                         ^