const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    // Write your code here
    while(line = await readline()){
        let tokens = line.split(' ').map(a=>parseInt(a)).sort((a,b)=>a-b);
        
        console.log(2*tokens[1]-tokens[0]);
    }
}()

这题真是莫名其妙的……