const N=1 shl 9;
var p,k:longint;
    f,g:text;
function zero (l:integer):integer;
var s:integer;
begin
s:=0;
while l<>0 do begin
s:=s+l div 5;
l:=l div 5;
end;
zero:=s;
end;
function fact (p:integer):integer;
var i,pas:integer;
begin
pas:=N;
i:=0;
while pas<>0 do begin
if zero(i+pas)<p then
i:=i+pas;
pas:=pas shr 1
end;
fact:=i+1;
end;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
k:=fact(p);
write(g,k);
close (f);
close (g);
end.