var o,i,ot,n,j,k:int64;
    jo:boolean;

    f,g:text;
procedure te;
begin
o:=0;
while j mod 5=0 do begin
j:=j div 5;
o:=o+1;
end;

end;


begin
assign(f,'fact.in');reset(f);
readln(f,k); close(f);

jo:=true;
n:=k;
while jo do begin
n:=n+1;

ot:=0;
i:=2;
while i<=n do begin
j:=i;
te;
ot:=ot+o;
inc(i);
end;

{writeln(ot); }
if ot>=k then jo:=false;
end;

assign(g,'fact.out');rewrite(g);
if k=0 then writeln(g,1)
else
if ot=k then writeln(g,n)
        else writeln(g,-1);

close(g);

end.