program dasda;
var nz,p,q,k,i:longint;
f,g:text;
begin
assign (f,'fact.in');
reset (f);
assign (g,'fact.out');
rewrite (g);
readln (f,k);
p:=1;
nz:=0;
while nz<k do begin
                p:=p*i;
                i:=i+1;
                if (p mod 5=0) and (p mod 2=0) then begin nz:=nz+1;
                                                          p:=1;
                                                          end;
                end;
writeln (g,i-1);
close (f);
close (g);
end.