program fact;
 var a:array [1..50000]of longint;
     i,k1,k,n,k2:longint;
     fi,fo:text;
begin assign(fi,'fact.in');
      assign(fo,'fact.out');
      reset(fi);
      rewrite(fo);
      read(fi,k);
      a[1]:=25;
      if k<=1 then n:=1 else begin for i:=2 to 11 do a[i]:=a[i-1]*5;
                                           n:=k*5;
                                           for i:=1 to 10 do if n>=a[i] then k2:=i;
                                           for i:=1 to k2 do k2:=k2*5;
                                           n:=n-k2;
                             end;
      if k=5 then n:=1;
      write(fo,n);
      close(fo);
end.