foo.cc: In function 'int main()':
foo.cc:4:5: error: 'scanf' was not declared in this scope
    4 |     scanf("%d",&n);
      |     ^~~~~
foo.cc:24:5: error: 'printf' was not declared in this scope
   24 |     printf("%d",ans);
      |     ^~~~~~
foo.cc:2:1: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?
    1 | #include<cstdlib>
  +++ |+#include <cstdio>
    2 | int n, arr[4005];

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