var p,n:longint;
    f:text;
begin
assign(f,'fact.in');
reset(f);
read(f,p);
close(f);
assign(f,'fact.out');
rewrite(f);
if p=0 then write(f,'1')
       else n:=p*5;
if n>25 then n:=n-5;
if n>125 then n:=n-5;
if n>625 then n:=n-5;
if n>3125 then n:=n-5;
if n>15625 then n:=n-5;
if n>78125 then n:=n-5;
if n>390625 then n:=n-5;
if n>1953125 then n:=n-5;
if n>9765625 then n:=n-5;
if n>48828125 then n:=n-5;
if n>244140625 then n:=n-5;
if n>1220703125 then n:=n-5;
write(f,n);
close(f);
end.