class Problem0064:
    def solve(this):        
        res = {}
        for ch in list(input()):
            res[ch] = res.get(ch, 0) + 1
        for ch in list(input()):
            res[ch] = res.get(ch, 0) + 1

        for v in res.values():
            if v != 2:
                print("NO")
                return
        print("YES")

if __name__ == "__main__":
    problem = Problem0064()
    problem.solve()