var f,g:text;
    p,fact2,fact5,i,aux:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
close(f);
fact2:=0;fact5:=0;
if p=0 then
begin
     write(g,1);
     close(g);
     halt;
end;
if p=1 then
begin
     write(g,5);
     close(g);
     halt;
end;
i:=0;
while  fact5<p do
begin
     i:=i+1;
     aux:=i;
     while aux mod 5=0 do
     begin
          fact5:=fact5+1;
          aux:=aux div 5;
    end;
    if  fact5=p then
    begin
         write(g,i);
         close(g);
         halt;
    end;
end;
write(g,-1);
close(g);
end.