process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = []
var reader = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
});

reader.on('line', (line) => {
    lines.push(line);
});

reader.on('close', () => {
    var A = parseInt(lines[0]);
    var B = parseInt(lines[1]);
    var C = parseInt(lines[2]);
    var D = parseInt(lines[3]);
    newArr = [A,B,C,D];
    newArr.sort();
    if(newArr[3] - newArr[2] == 1 && newArr[2] - newArr[1] == 1 && newArr[1] - newArr[0] == 1){
        console.log('Yes');
    } else {
        console.log('No');
    }
});