integer n,i
read *,n

if(n.lt.0)then
print *,"n on neg."
stop
endif
	if(n.eq.0)then
ifakt=1
print 100,ifakt
stop
100	format("fakt0=",I10)  
endif
ifact=1
do i=2,n
ifact=ifact*i
enddo
print 100,ifact
stop
end