CompileError!

main.cpp: In function \xe2\x80\x98int main()\xe2\x80\x99:\nmain.cpp:40:23: warning: comparison of integer expressions of different signedness: \xe2\x80\x98int\xe2\x80\x99 and \xe2\x80\x98std::__cxx11::basic_string<char>::size_type\xe2\x80\x99 {aka \xe2\x80\x98long unsigned int\xe2\x80\x99} [-Wsign-compare]\n   40 |     for (int i = 0; i < s.size(); ++i) {\n      |                     ~~^~~~~~~~~~\nmain.cpp:46:25: warning: comparison of integer expressions of different signedness: \xe2\x80\x98int\xe2\x80\x99 and \xe2\x80\x98std::__cxx11::basic_string<char>::size_type\xe2\x80\x99 {aka \xe2\x80\x98long unsigned int\xe2\x80\x99} [-Wsign-compare]\n   46 |         if (i == 0 || i == s.size() - 1) {\n      |                       ~~^~~~~~~~~~~~~~~\nmain.cpp: At global scope:\nmain.cpp:67:2: error: expected unqualified-id before numeric constant\n   67 | }2\n      |  ^\n