输出有空格，包括,和b之间

注意,注意

cout这么写:

cout<<"w("<<a<<", "<<b<<", "<<c<<")"<<" "<<"="<<" "<<w(a,b,c)<<endl;

printf这么写:

printf("w(%lld, %lld, %lld) = %lld\n", a, b, c,w(a, b, c));