/in/foo.cc: In function 'int main()':
/in/foo.cc:60:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d",&n,&m,&l,&k);
                               ^
/in/foo.cc:63:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&x),a[x]=1;
                        ^
/in/foo.cc:66:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&x),b[x]=1;
                        ^
/in/foo.cc:69:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&x,&y);
                      ^