4 50
10 60
20 100
30 120
15 90

240.0

n, W = map(int, input().split())
items = []
for _ in range(n):
    w, v = map(int, input().split())
    items.append((w, v))
items.sort(key=lambda x: x[1]/x[0], reverse=True)
total = 0.0
for w, v in items:
    if W <= 0:
        break
    take = min(w, W)
    total += take * v / w
    W -= take
print(round(total, 1))