View Compilation Error

0_0_17820854_22558.cpp: In function 'int main()':
0_0_17820854_22558.cpp:19:18: error: 'scanf' was not declared in this scope
     scanf("%d",&t);
                  ^
0_0_17820854_22558.cpp:27:27: error: 'memset' was not declared in this scope
         memset(flag,0,1000);
                           ^
0_0_17820854_22558.cpp:43:26: error: 'printf' was not declared in this scope
         printf("%d\n",sum);
                          ^