View Compilation Error

0_0_15304996_11728.cpp: In function 'int main()':
0_0_15304996_11728.cpp:20:18: error: 'scanf' was not declared in this scope
     scanf("%d",&k);
                  ^
0_0_15304996_11728.cpp:33:37: error: 'memset' was not declared in this scope
         memset(vis,false,sizeof(vis));
                                     ^
0_0_15304996_11728.cpp:41:28: error: 'printf' was not declared in this scope
         printf("%d\n",n-sum);
                            ^