/in/foo.cc: In constructor 'BigInt::BigInt(const char*)':
/in/foo.cc:39:13: error: 'strlen' was not declared in this scope
   39 |         n = strlen(s);
      |             ^~~~~~
/in/foo.cc:2:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | #include <string>
/in/foo.cc: In member function 'BigInt BigInt::operator*(const BigInt&)':
/in/foo.cc:89:9: error: 'memset' was not declared in this scope
   89 |         memset(result.p, 0, sizeof(int) * (n + obj.n));
      |         ^~~~~~
/in/foo.cc:89:9: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?