answer.code: In function ‘int main()’:
answer.code:10:9: error: ‘printf’ was not declared in this scope
   10 |         printf("%.6f", sum);
      |         ^~~~~~
answer.code:2:1: note: ‘printf’ is defined in header ‘<cstdio>’; did you forget to ‘#include <cstdio>’?
    1 | #include<iostream>
  +++ |+#include <cstdio>
    2 | using namespace std;