/in/foo.cc: In function 'int chk(int)':
/in/foo.cc:23:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  int tlen=n+m>>1;
           ~^~
/in/foo.cc: In function 'int main()':
/in/foo.cc:7:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,j,k) for (int i = j ; i < k+1 ; ++i)
                                       ^
/in/foo.cc:43:3: note: in expansion of macro 'rep'
   rep(a,2,strlen(strt+1))
   ^~~