<gh_stars>0
def geomtrcD(n,p):
    return ((1-p)**(n-1)) * p

if __name__ == '__main__':
    [nr, dr] = [int(i) for i in raw_input().strip().split()]
    n = int(raw_input())
    p = nr*1.0 / dr
    count = 0
    for i in xrange(1,n+1):
        count += geomtrcD(i,p)
    print "{0:0.3f}".format(count)