/in/foo.c: In function 'main':
/in/foo.c:23:2: warning: implicit declaration of function 'jj' [-Wimplicit-function-declaration]
  jj(a1,a2,n1,n2);
  ^~
/in/foo.c: At top level:
/in/foo.c:27:6: warning: conflicting types for 'jj'
 void jj(int a1[],int a2[],int n1,int n2)
      ^~
/in/foo.c:23:2: note: previous implicit declaration of 'jj' was here
  jj(a1,a2,n1,n2);
  ^~