foo.cc: In function 'int main()':
foo.cc:39:15: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'int' [-Wformat=]
   scanf("%d",x);
               ^
foo.cc:34:10: warning: unused variable 'n1' [-Wunused-variable]
  int num,n1,n2,L,k,n;
          ^~
foo.cc:39:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",x);
   ~~~~~^~~~~~~~
foo.cc:39:8: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   scanf("%d",x);
   ~~~~~^~~~~~~~

[Hydro](https://hydro.ac)提供评测服务