foo.cc: In function 'bool init(int, int, int)':
foo.cc:4:20: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
 #define inf (1<<21)-1
             ~~~~~~~^~
foo.cc:38:12: note: in expansion of macro 'inf'
  int o=g[x&inf];
            ^~~
foo.cc:4:20: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
 #define inf (1<<21)-1
             ~~~~~~~^~
foo.cc:51:40: note: in expansion of macro 'inf'
  a[r].x=x;a[r].y=y;a[r].i=i;a[r].n=g[x&inf];g[x&inf]=r;
                                        ^~~
foo.cc:4:20: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
 #define inf (1<<21)-1
             ~~~~~~~^~
foo.cc:51:49: note: in expansion of macro 'inf'
  a[r].x=x;a[r].y=y;a[r].i=i;a[r].n=g[x&inf];g[x&inf]=r;
                                                 ^~~
foo.cc: In function 'int main()':
foo.cc:60:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&sou);
  ~~~~~^~~~~~~~~~~
foo.cc:61:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&des);
  ~~~~~^~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。