import sys
readline=sys.stdin.readline

F,N,K=map(int,readline().split())
fact=[1]
for i in range(1,N+1):
    fact.append(fact[-1]*i)
K=N-K
ans=0
for i in range(K+1):
    for j in range(K+1,N+1):
        for f in range(F):
            ans+=pow(f,i)*pow(F-f-1,N-j)*(f+1)/(fact[i]*fact[j-i]*fact[N-j])
ans*=fact[N]
ans/=pow(F,N)
print(ans)