/in/foo.cc: In function 'void build_t(int)':
/in/foo.cc:49:22: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  ls.l=fa.l; ls.r=fa.l+fa.r>>1;
                  ~~~~^~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:126:15: warning: unused variable 'opt' [-Wunused-variable]
  for(R II i=1,opt;i<=q;i++) {
               ^~~