/in/foo.c: In function 'insert':
/in/foo.c:31:12: warning: array subscript has type 'char' [-Wchar-subscripts]
    s[k+1]=s[k];
            ^
/in/foo.c:32:4: warning: array subscript has type 'char' [-Wchar-subscripts]
   s[j]=',';
    ^
/in/foo.c: In function 'main':
/in/foo.c:42:2: error: too many arguments to function 'insert'
  insert(s,num);
  ^~~~~~
/in/foo.c:23:6: note: declared here
 void insert(char s[])
      ^~~~~~