n, k, x, *a = map(int, open(0).read().split())
b = [a[i]-x*(i+1)+(i>=k)*a[i] for i in range(n)]
c = n-1-b[::-1].index(max(b))
print(sum(sorted(a[:c+1])[::-1][:min(k, c+1)])-(c+1)*x)