#!/c/Python34/python
# coding: utf-8


def main():
    A, B, T = map(int, input().split())
    ans = 10**10
    if A < B:
        A, B = B, A
    i = 0
    while A*i <= T and i <= B:
        dif = T - A*i
        j = dif//B
        if dif % B != 0:
            j += 1
        ans = min(ans, A*i+B*j)
        i += 1
    print(ans)


if __name__ == '__main__':
    main()