import sys
input=sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    L=LI()
    L.sort()
    flag=1
    for i in range(3):
        if L[i+1]-L[i]!=1:
            flag=0
            break
        
    if flag:
        print("Yes")
    else:
        print("No")
        


main()