def floor_sum(n,m,a,b):
    res = 0
    while True:
        res += ((n-1)*n*(a//m)//2) + (b//m)*n
        a %= m
        b %= m
        if a*n+b <= m:
            return res
        Y = (a*n+b)//m
        n,m,a,b = Y,a,m, a*n + b - m*Y

"""
ax + by <= t, x >= 0, y >= 0 をみたす x,y の個数
"""
def points_in_triange(a,b,t):
    return floor_sum(1+t//a,b,a,t-t//a*a) + t//a + 1

a,b,t = map(int,input().split())
r = points_in_triange(a,b,t-1)
ng = t-1
ok = 10**12
while ok-ng > 1:
    mid = (ok+ng)//2
    if r < points_in_triange(a,b,mid):
        ok = mid
    else:
        ng = mid
print(ok)