const speed = parseInt(readline());
const lightCount = parseInt(readline());
const isGreen = (sp, tl) => Math.floor(Math.round(tl.distance / (sp * 1000 / 3600)) / tl.duration) % 2 == 0;
let s = [];

for (let i = 0; i < lightCount; i++) {
    var [distance, duration] = readline().split(' ').map(i => parseInt(i));
    s.push({ duration, distance });
}

for (let as = speed; as > 0; as--) {
    if (s.every(tl => isGreen(as, tl))) {
        console.log(as);
        break;
    }
}