var     p,n,rez : longint;
        k:boolean;

function nrzerouri(x:longint):longint;
var     i,xx,nr:longint;
begin
nr:=0;
i:=5;
xx:=1;
while i <= x do
        begin
        inc(nr,x div i);
        i:=i*5;
        end;
nrzerouri:=nr;
end;

procedure bsearch(a,b:longint);
var c,x: longint;
begin

while a<= b do
        begin
        c:=(a+b) div 2;
        x:=nrzerouri(c);
        if x  >= p then
                begin
                if x = p then
                        rez:=c;
                b:=c-1;
                end
        else
                a:=c+1;
        end;

end;

begin
assign(input,'fact.in'); reset(input); readln(p); close(input);
rez:=-1;
if p = 0 then rez:=1
else
bsearch(1,500000015);
//if (rez <> -1) and ( rez <> 1)  then rez := rez  - rez mod 5;
assign(output,'fact2.out'); rewrite(output);

writeln(rez);
close(output);
//writeln(10*10*10*10*10*10*10*10);}
end.