/in/foo.cc: In function 'int main()':
/in/foo.cc:8:9: warning: unused variable 'm' [-Wunused-variable]
  int n, m, gap=0, x, y;
         ^
/in/foo.cc:20:22: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<a[x]<<" "<<a[y];
                      ^
/in/foo.cc:20:14: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<a[x]<<" "<<a[y];
              ^~~