foo.cc: In function 'bool check(int)':
foo.cc:10:5: error: 'memset' was not declared in this scope
   10 |     memset(diff,0,sizeof(diff));
      |     ^~~~~~
foo.cc:2:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | using namespace std;

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