foo.cc: In function ‘int main()’:
foo.cc:14:13: warning: argument to variable-length array is too large [-Wvla-larger-than=]
   14 |         int a[n-1];
      |             ^
foo.cc:14:13: note: limit is 9223372036854775807 bytes, but argument is 18446744073709551612
foo.cc:28:23: warning: ‘y1’ may be used uninitialized [-Wmaybe-uninitialized]
   28 |         for(int i=y1;i<n-1;i++)
      |                      ~^~~~
foo.cc:20:20: note: ‘y1’ was declared here
   20 |         int y=a[0],y1;
      |                    ^~