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n,k,t=input().split(" ")
k=int(k)
t = int(t)
m = list(input())
if k<m.count("1"):
    if (m.count("3")-t*2+k)<0:
        print("-1")
    else:
        print(m.count("3")-t*2+k)
else:
    if k<=m.count("1")+m.count("2"):
        print(m.count("3")+k-m.count("2")+m.count("1"))
    else:
        print(n)