/in/foo.cc: In function 'void Search2(int, int, int*, bool)':
/in/foo.cc:24:29: warning: unused variable 'j' [-Wunused-variable]
     int c=(a[0]+a[1]+u)%n,i,j;
                             ^
/in/foo.cc: At global scope:
/in/foo.cc:63:3: error: expected unqualified-id before 'if'
   if(num[x]==-1)//如果字母未被确定 
   ^~