# 時間で解決め打ち二分探索できるか

V, T, P = map(int, input().split())

def check(t):
    v = 0
    v += V
    v += V*P
    v += (t-1)//T+1
    if v > t:
        return 1
    else:
        return 0
    
#for t in range(0, 30):
#    print(t, check(t))
    
OK = 0
NG = 10**20
while (NG-OK)>1:
    mid = (NG+OK)//2
    if check(mid) == 1:
        OK = mid
    else:
        NG = mid
print(NG)