/in/foo.cc: In function 'void ac::init()':
/in/foo.cc:31:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j = 0; j < t[i].size(); ++j) {
                    ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void ac::work()':
/in/foo.cc:62:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < s.size(); ++i) {
                   ~~^~~~~~~~~~