A, B, C, D, E = map(int, input().split())

n = B - C
X = D

P = 0
i = 1
for _ in range(1, n+1):
    for _ in range(A):
        if i % 10 == 0 and E <= X:
            X -= E
        P += X
        i += 1
    
print(P)