program main
IMPLICIT none
    INTEGER :: n,i,f,j
    REAL :: t,s=0,a
    PRINT *,"ENTER NUMBER of terms and contsant"
    read *,n,a
    do i=1,n
    f=1
    do j=1,i
    f=f*j
    enddo
    t=a**i/f
    s=s+t
    enddo
    PRINT*,"sum=",s
end