#!/usr/bin/env python
# -*- coding: utf-8 -*-

A,B,T = map(int,input().split())
ans = 10**10

for i in range(A):
    if B*i > T:
        if abs(T-ans) > abs(T-B*i):
            ans = B*i
        break
    x = ((T-B*i)+A-1)//A
    if abs(T-ans) > abs(T-A*x-B*i):
        ans = A*x + B*i
print(ans)