import math
N = int(input())
min = N-100
max = N+100
min_s = math.sqrt(min)

if min != 2 and min % 2 == 0:
    print(min)
elif min == 2 or min == 1:
    print(4)
elif min % 2 == 1:
    for i in range(3, min, 2):
        if i > min_s:
            ans = min + 1
            break
        elif min % i != 0:
            continue
        elif min % i == 0:
            ans = min
            break
    print(ans)