/in/foo.c: In function 'noco':
/in/foo.c:4:6: warning: unused variable 'first' [-Wunused-variable]
  int first,i,j,k=0;
      ^~~~~
/in/foo.c: In function 'main':
/in/foo.c:29:16: warning: variable 'm' set but not used [-Wunused-but-set-variable]
  int a[20],n,i,m;
                ^
/in/foo.c:29:14: warning: unused variable 'i' [-Wunused-variable]
  int a[20],n,i,m;
              ^