/in/foo.cc: In function 'void readnum(int&)':
/in/foo.cc:15:2: warning: this 'while' clause does not guard... [-Wmisleading-indentation]
  while (ch=getchar(),ch<'0'||ch>'9');x=x*10+ch-'0'; 
  ^~~~~
/in/foo.cc:15:38: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'while'
  while (ch=getchar(),ch<'0'||ch>'9');x=x*10+ch-'0'; 
                                      ^
/in/foo.cc: In function 'bool YiCheck(int)':
/in/foo.cc:73:6: warning: unused variable 'cnt' [-Wunused-variable]
  int cnt=0,maxw=0;
      ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:102:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   if (YiCheck(l+r>>1)) r=l+r>>1;
               ~^~
/in/foo.cc:102:27: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   if (YiCheck(l+r>>1)) r=l+r>>1;
                          ~^~
/in/foo.cc:103:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   else l=(l+r>>1)+1;
           ~^~