/in/foo.cc: In function 'int main()':
/in/foo.cc:12:31: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   12 |             for (int i = 0; i < strlen(input); ++i) {
      |                             ~~^~~~~~~~~~~~~~~