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

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

for i in range(A):
    x = max(((T-B*i)+A-1)//A,0)
    if abs(T-ans) > abs(T-A*x-B*i):
        ans = A*x + B*i
    if B*i > T:
        break
print(ans)