from sys import stdin
def main():
    #入力
    readline=stdin.readline
    l=list(map(int,readline().split()))
    l.sort()

    for i in range(1,4):
        if l[i]!=l[i-1]+1:
            print("No")
            break
    else:
        print("Yes")

if __name__=="__main__":
    main()