View Compilation Error

0_0_19699303_22158.cpp: In function 'int main()':
0_0_19699303_22158.cpp:5:20: error: 'scanf' was not declared in this scope
 while(scanf("%d",&n)!=EOF)
                    ^
0_0_19699303_22158.cpp:5:23: error: 'EOF' was not declared in this scope
 while(scanf("%d",&n)!=EOF)
                       ^
0_0_19699303_22158.cpp:9:27: error: 'printf' was not declared in this scope
 if(n==1)printf("%d\n",a[0]);
                           ^
0_0_19699303_22158.cpp:16:16: error: 'printf' was not declared in this scope
 printf("%d\n",s);
                ^