/in/foo.cc: In function 'void del(int)':
/in/foo.cc:7:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < s.size(); i++) {
                  ~~^~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:14:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < s.size(); i++) {
                  ~~^~~~~~~~~~
/in/foo.cc:15:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (s[i]<s[i+1] || i == s.size()-1) {
                      ~~^~~~~~~~~~~~~
/in/foo.cc:21:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (t == s.size()) cout << 0;
      ~~^~~~~~~~~~~
/in/foo.cc:22:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (; t < s.size(); t++) cout << s[t];
         ~~^~~~~~~~~~