INF = 10 ** 7
import sys
input = sys.stdin.readline
sys.setrecursionlimit(100000000)
dy = (-1,0,1,0)
dx = (0,1,0,-1)
from bisect import bisect_left

def main():
    x = list(map(int,input().split()))
    x.sort()
    flag = True
    for i in range(3):
        if x[i + 1] - x[i] != 1:
            flag = False
    
    if flag:
        print('Yes')
    else:
        print('No')

if __name__ == '__main__':
    main()