#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
nums = sorted(map(int, read().split()))


# %%
is_ok = all(y == x + 1 for x, y in zip(nums, nums[1:]))
print('Yes' if is_ok else 'No')