from math import ceil

A,B,T = list(map(int, input().split(' ')))

maxa = ceil(T/A)
maxb = ceil(T/B)

solution = float('inf')
for a in range(maxa+1):
    for b in range(maxb+1):
        total = b * B + a * A
        if T <= total:
            solution = min(solution, total)
print(solution)