var d,j,p,x:integer;
f,g:text;
begin
assign(f,'fact.in');
reset(f);
readln(f,p);
close(f);

if p=0 then begin writeln(1); exit; end;
x:=0;

repeat
x:=x+5;
if x mod 5=0 then begin
d:=x;
j:=1;
repeat
d:=d div 5;
if d mod 5=0 then
inc(j);
until d mod 5<>0;
p:=p-j;
end
else
p:=p-1;
until p<=0;
assign(g,'fact.out');
rewrite(g);
writeln(x);
close(G);
readln;
end.