let fs = require('fs');
let input = fs.readFileSync('/dev/stdin').toString().split(" ");
const x = Number(input[0]);
const y = Number(input[1]);
const w = Number(input[2]);
const h = Number(input[3]);
const array = [x, w-x, y, h-y];
const answer = Math.min(...array);
console.log(answer);