View Compilation Error

0_0_20032177_31154.cpp: In function 'int main()':
0_0_20032177_31154.cpp:16:32: error: 'scanf' was not declared in this scope
   while(scanf("%d%d%d",&a,&b,&n)!=EOF)
                                ^
0_0_20032177_31154.cpp:16:35: error: 'EOF' was not declared in this scope
   while(scanf("%d%d%d",&a,&b,&n)!=EOF)
                                   ^
0_0_20032177_31154.cpp:19:33: error: 'printf' was not declared in this scope
         printf("%d\n",Dan(a,b,n));  
                                 ^