m,n,b=map(eval,input().split())
d=m
for i in range(n):
m=m+m*b
a=m-d
print("interest=%0.2f"%a)
12-02
1726

03-17
m,n,b=map(eval,input().split())
d=m
for i in range(n):
m=m+m*b
a=m-d
print("interest=%0.2f"%a)