foo.cc: In function 'int main()':
foo.cc:5:12: warning: unused variable 'j' [-Wunused-variable]
    5 |  int n,k,i,j;
      |            ^
foo.cc:5:10: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
    5 |  int n,k,i,j;
      |          ^
foo.cc:10:15: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
   10 |   while(j<=n-i+k)
      |            ~~~^~

[Hydro](https://hydro.ac)提供评测服务