for loop

[Shawn Minisall]

    #Intro
    print "*********************************************"
    print  "WELCOME TO THE POPULATION GROWTH CALCULATOR"
    print "*********************************************"

    print "This program will predict the size of a population of organisms."
    print
    print
    organisms=input("Please enter the starting number of organisms: ")

    increase=input("Please enter the average daily population increase 
as a percentage (20% = .20): ")

    days=input("Please enter the number of days that they will multiply: ")
    
print "         Day                                    Population"
print "----------------------------------------------------------"


for p in range (days):

    population = organisms * population * increase

    print days,

    print "\t\t\t\t",population

I'm having problems with my for loop here to calculate estimated 
population output to a table.  Instead of knowing how much I want to 
loop it, the loop index is going to be whatever number of days the user 
enters.  When I run my program, it asks the 3 questions above but then 
just dead stops at a prompt which leads me to believe there's something 
wrong with my loop.  I have the exact same setup in another program, but 
the loop index has a specific value.  I tried (0,days), (1,days) ect. 
and I don't think for loops need accumulators, I've tried it with one 
anyways and it still stops. 

Any idea's?

thx