program factorial2
    implicit none
    integer::i,n,factor
    
    print *, "input the limit to calculate factoriel of numbers from 2 ~ limit:"
    do
        read *,n
        if (n>=2)exit
        print *,'the number is less than 2. enter another number.'
    end do
    factor = 1
    do i =2,n
        factor = factor*i
        print*,i,'!=',factor
    end do
end program factorial2