var p,nr2,nr5,i,ii:longint;
    f:text;
begin
assign (f,'fact.in');
reset (f);
readln (f,p);
close (f);
if p=0 then
begin
assign (f,'fact.out');
rewrite (f);
writeln (f,1);
close(f);
end
else
begin
i:=5;
nr5:=0;
nr2:=0;
while (nr5<>p)and(i>0) do
begin
ii:=i;
while ii<>0 do
if ii mod 5=0 then
begin
inc (nr5);
ii:=ii div 5;
if ii mod 5=0 then inc(nr2);
end
else
break;
inc (i,5);
end;
if nr5=p then
begin
assign (f,'fact.out');
rewrite (f);
writeln (f,5*(nr5-nr2));
close(f);
end;
end;
end.