import sys
input = sys.stdin.readline

A,B,C,D,E=map(int,input().split())
k=(B-C)*A
DP=[D]

for i in range(1000):
    X=DP[-1]
    if (i+2)%10!=0:
        DP.append(X)
    elif E<=X:
        DP.append(X-E)
    else:
        DP.append(X)


S=[0]
for i in range(1000):
    S.append(S[-1]+DP[i])

print(S[k])