function Main(input) {
	input = input.split(" ");
	
	var C1=input[0];
	var C2=input[1];
	
	if(Math.abs(C1.charCodeAt(0)-C2.charCodeAt(0))==1){
	  console.log("Yes");
	}else{
	  console.log("No");
	}
	

}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));