"""

"""

import sys
from sys import stdin

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

N = A * (B-C)

ans = 0

for i in range(2,N+2):

    ans += D

    if i % 10 != 0:
        D = D
    elif i % 10 == 0 and E <= D:
        D = D -E
    else:
        D = D

print (ans)