A,B,C,D,E=map(int,input().split())
H=B-C
AMDM=A*H
ans=0
pre=0
for i in range(1,AMDM+1):
    if(i==1):
        ans+=D
        pre=D
    elif(i%10):
        ans+=pre
    elif(E<=pre):
        ans+=pre-E
        pre=pre-E
    else:
        ans+=pre
print(ans)