/in/foo.cc: In function 'int main()':
/in/foo.cc:29:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < peaks.size(); ++i) {
                     ~~^~~~~~~~~~~~~~
/in/foo.cc:30:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         cout << peaks[i] << (i < peaks.size() - 1 ? " " : "");
                              ~~^~~~~~~~~~~~~~~~~~