"""File:     cpd_int2.py
   Purpose:  Compute the amount of a principal given an interest
             rate, the time in years, and the number of periods per
             year

   Run:      python cpd_int.py

   Input:    Principal (decimal fraction)
             Interest rate (decimal fraction)
             Time in years (decimal fraction)
             Periods per year (whole number)
   Output:   The amount
"""

#----------------------------------------------------------------------
def cpd_int(P, r, t, y):
   """ Find the amount of a principal P invested for t years at
   interest rate r and compounded y times per year.
   """
   n = t*y
   s = r/y
   A = P*(1+s)**n
   return A


#----------------------------------------------------------------------
# Program starts executing here
P = float(raw_input("Enter the principal\n"))
r = float(raw_input("Enter the interest rate (decimal fraction)\n"))
t = float(raw_input("Enter the number of years (decimal fraction)\n"))
y = int(raw_input("Enter the number of periods per year (whole number)\n"))

A = cpd_int(P, r, t, y)
print "If", "$%.2f" %P, "is invested for", t, "years at interest"
print "   rate", r, "(per year), and compounded", y, "times per year,"
print "   then the amount will be", "$%.2f"%A