#!/usr/bin/env python3


def judge(xs):
    ys = sorted(xs)
    return all(yj - yi == 1 for yi, yj in zip(ys[:-1], ys[1:]))


def main():
    xs = (int(x) for x in input().split())
    if judge(xs):
        print("Yes")
    else:
        print("No")


if __name__ == "__main__":
    main()