소프티어

const fs = require('fs');

const [NM, ...input] = fs.readFileSync(0, 'utf8').trim().split('\n');
const [N, M] = NM.split(' ').map(Number);
const sectionsA = input.slice(0, N).map(v => v.split(' ').map(Number));
const sectionsB = input.slice(N).map(v => v.split(' ').map(Number));

let max = 0;
let [Aindex, Bindex] = [0, 0];

while (sectionsA[Aindex] !== undefined && sectionsB[Bindex] !== undefined) {
    const minRange = Math.min(sectionsA[Aindex][0], sectionsB[Bindex][0]);

    const speedDif = sectionsB[Bindex][1] - sectionsA[Aindex][1];
    max = Math.max(max, speedDif);

    // 범위 갱신
    sectionsA[Aindex][0] -= minRange;
    sectionsB[Bindex][0] -= minRange;

    // 인덱스 이동
    if (sectionsA[Aindex][0] === 0) Aindex++;
    if (sectionsB[Bindex][0] === 0) Bindex++;
}

console.log(max);