/in/foo.cc: In function 'int main()':
/in/foo.cc:16:13: error: '__gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> > >::value_type {aka class std::__cxx11::basic_string<char>}' has no member named 'contains'
    if (S[i].contains(S[j]))
             ^~~~~~~~