import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


F,N,K = MI()

fac = [1]
for i in range(1,N+1):
    fac.append(fac[-1]*i)

ans = 0
for x in range(1,F+1):
    e = 0
    p = (x-1)/F
    q = (F-x)/F
    r = 1/F
    for i in range(N-K+1):  # x-1以下の個数
        for j in range(K):  # x+1以上の個数
            k = N-(i+j)  # xの個数
            e += (fac[N]//fac[i]//fac[j]//fac[k])*pow(p,i)*pow(q,j)*pow(r,k)
    ans += x*e

print(ans)