View Compilation Error

0_0_37100488_22610.cpp: In function 'int main()':
0_0_37100488_22610.cpp:6:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                        ^
0_0_37100488_22610.cpp:6:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                           ^
0_0_37100488_22610.cpp:8:17: error: 'getchar' was not declared in this scope
         getchar();
                 ^
0_0_37100488_22610.cpp:11:19: error: 'gets' was not declared in this scope
             gets(a);
                   ^
0_0_37100488_22610.cpp:35:34: error: 'printf' was not declared in this scope
             if(k>=3){printf("YES");}
                                  ^
0_0_37100488_22610.cpp:36:30: error: 'printf' was not declared in this scope
             else {printf("NO");}
                              ^
0_0_37100488_22610.cpp:38:31: error: 'printf' was not declared in this scope
             else printf("NO\n");
                               ^