program fact;
var f:text;
    p,n,i,j:longint;
    v:array[1..10] of longint;

begin
     assign(f,'fact.in');
     reset(f);
     readln(f,p);
     close(f);
     n:=5*p;
     i:=25;
     v[1]:=1;
     while(i<=n) do
     begin
          n:=n-5;
          j:=1;
          while(v[j] mod 5 = 0) do
          begin
               n:=n-5;
               v[j+1]:=v[j+1]+1;
               j:=j+1;
          end;
          i:=i+25;
          v[1]:=v[1]+1;
     end;

     assign(f,'fact.out');
     rewrite(f);
     writeln(f,n);
     close(f);
end.