program   factoriale;
var       n,s,p,a,i:integer;

begin
write('p='); readln(p);
n:=p; i:=5; s:=0;
while i<=n do
        begin
        a:=i;
        while a mod 5=0 do
                begin
                s:=s+1;
                a:=a div 5;
                end;
        i:=i+5
        end;
if s<p then
        begin
        n:=n+1;
        s:=0;
        end
else writeln('s=', s);
end.