/in/foo.cc: In function 'int main()':
/in/foo.cc:29:15: error: 'strlen' was not declared in this scope
   29 |    int lena = strlen(a[i]);
      |               ^~~~~~
/in/foo.cc:2:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    1 | #include<iostream>
  +++ |+#include <cstring>
    2 | using namespace std;
/in/foo.cc:45:44: error: 'strlen' was not declared in this scope
   45 |    if (num[0] == num[i]&& char_to_int(a[0],strlen(a[0]))> char_to_int(a[i], strlen(a[i]))) {
      |                                            ^~~~~~
/in/foo.cc:45:44: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?