import sys

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


def main():
    A = [int(x) for x in input().split()]
    A.sort()
    for i, j in zip(A, A[1:]):
        if j - i != 1:
            print("No")
            break
    else:
        print("Yes")


if __name__ == '__main__':
    main()