/in/foo.cc: In function 'int main()':
/in/foo.cc:56:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int l=0;l<st.size();l++)
              ~^~~~~~~~~~
/in/foo.cc:63:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int r=0;r<st.size();r++)
               ~^~~~~~~~~~
/in/foo.cc:75:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int l=0;l<st.size();l++)
               ~^~~~~~~~~~
/in/foo.cc:82:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int r=0;r<st.size();r++)
                ~^~~~~~~~~~
/in/foo.cc:89:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int t=0;t<st.size();t++)
                 ~^~~~~~~~~~
/in/foo.cc:102:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int l=0;l<st.size();l++)
               ~^~~~~~~~~~
/in/foo.cc:105:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int r=0;r<st.size();r++)
                ~^~~~~~~~~~