var answer = function(A,B,C,D){
    var arr = [A,B,C,D];
    arr.sort();
    var numA = arr[0];
    var numB = arr[1];
    var numC = arr[2];
    var numD = arr[3];
    if(numD - numC == 1 && numC - numB == 1 && numB - numA == 1){
        console.log('Yes');
    } else {
        console.log('No');
    }
}

answer(5,7,3,9);