foo.c: In function ‘main’:
foo.c:9:16: warning: variable ‘n2’ set but not used [-Wunused-but-set-variable]
    9 |         int n1,n2;
      |                ^~
foo.c:9:13: warning: variable ‘n1’ set but not used [-Wunused-but-set-variable]
    9 |         int n1,n2;
      |             ^~