/in/foo.cc: In function 'void Mul(std::vector<long long int>&, long long int)':
/in/foo.cc:6:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (long long i = 0; i < x.size(); ++i) {
                           ~~^~~~~~~~~~
/in/foo.cc:7:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (x[i] >= 10 && i == x.size() - 1)
                           ~~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'void Add(std::vector<long long int>&, const std::vector<long long int>&)':
/in/foo.cc:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (long long i = 0; i < x2.size(); ++i) {
                           ~~^~~~~~~~~~~