def gcd(x,y):
    while x%y:
        x,y=y,x%y
    return y

a,b,t=map(int,input().split())
if b>=10**3:
    ans=(t+a-1)//a*a
    c=0
    while t-b>0:
    	t-=b;c+=b
    	ans=min(ans,c+(t+a-1)//a*a)
    ans=min(c+b,ans)
else:
    ans=1<<60
    for i in range(b+1):
        k=max(0,t-a*i)
        ans=min(ans,i*a+(k+b-1)//b*b)
print(ans)