View Compilation Error

0_0_23911436_21409.cpp: In function 'int main()':
0_0_23911436_21409.cpp:3:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n)!=EOF){  
                        ^
0_0_23911436_21409.cpp:3:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&n)!=EOF){  
                           ^
0_0_23911436_21409.cpp:19:26: error: 'printf' was not declared in this scope
         printf("%d\n",k+1);  
                          ^