N = int(input())
for i in range(2, 100):
    L = [0] * 200
    L[0] = 1
    for j in range(1, 100):
        for k in range(1, i + 1):
            L[j] += L[j - k]
        if L[j] > N:
            break
        elif L[j] == N:
            print(i)
            exit()
    
print(-1)