Program 1;
var n,k2,k5,i,a:integer;
begin
write('n=');
read(n);
k2:=0;k5:=0;
for i:=2 to n do begin a:=i;
if a mod 2=0 then while a>=2 do
begin
a:=a div 2;
k2:=k2+1;
end;
a:=i;
if a mod 5=0 then while a>=5 do begin a:=a div 5;
k5:=k5+1; end; end;
if k2 write(k5);
readln
end.