View Compilation Error

0_0_20249526_28208.cpp:1:2: error: invalid preprocessing directive #nline
 #nline int GCD(int a, int b)  //不知道inline的同学可以百度一下，主要作用是提高函数效率。
  ^
0_0_20249526_28208.cpp:2:1: error: expected unqualified-id before '{' token
 {  
 ^
0_0_20249526_28208.cpp: In function 'int main()':
0_0_20249526_28208.cpp:9:38: error: 'scanf' was not declared in this scope
     while (scanf("%d %d", &step, &mod) != EOF)  
                                      ^
0_0_20249526_28208.cpp:9:43: error: 'EOF' was not declared in this scope
     while (scanf("%d %d", &step, &mod) != EOF)  
                                           ^
0_0_20249526_28208.cpp:11:40: error: 'printf' was not declared in this scope
         printf("%10d%10d    ", step,mod);    
                                        ^
0_0_20249526_28208.cpp:12:25: error: 'GCD' was not declared in this scope
         if(GCD(step, mod) == 1) printf("Good Choice\n\n");    
                         ^