#!/usr/bin/env python3

import sys


def divceil(a, b):
    return (a + b - 1) // b


def compute_min_amount(a, b, t):
    INF = sys.maxsize

    def amount(x):
        return b * x + a * divceil(t - b * x, a)
    answer = INF
    for x in range(a + 1):
        if x * b > t:
            break
        answer = min(answer, amount(x))
    return answer


def main():
    a, b, t = map(int, input().split())
    print(compute_min_amount(a, b, t))


if __name__ == '__main__':
    main()