foo.cc: In function 'int main()':
foo.cc:15:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |  for (int i = 0; i < s.length();)
      |                  ~~^~~~~~~~~~~~
foo.cc:19:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   19 |   for (j = 0; j < t.length();)
      |               ~~^~~~~~~~~~~~
foo.cc:29:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |   if (j == t.length())
      |       ~~^~~~~~~~~~~~~
foo.cc:31:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |    if (i+j <= s.length())
      |        ~~~~^~~~~~~~~~~~~

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