A, B, T = map(int, input().split())
ans = 10 ** 18
now = 0
while T - now * B >= 0 and now <= A:
    ans = min(ans, (T - now * B + A - 1)//A*A + now * B)
    now += 1
print(min(ans, (T + B - 1)//B*B))