/in/P4.cpp: In function 'int main()':
/in/P4.cpp:25:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int i = 0; i < numbers.size(); ++i) {
                     ~~^~~~~~~~~~~~~~~~
/in/P4.cpp:32:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int i = 0; i < numbers.size(); ++i) {
                     ~~^~~~~~~~~~~~~~~~
/in/P4.cpp:56:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int i = 0; i < result.size(); ++i) {
                     ~~^~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors