function gcd(a,b) {
 while(b !== 0) {
	 const r = a % b;
	 a = b;
	 b = r;
	 }
 return a;
}
function solve (x1,y1,x2,y2) {
	const yd = Math.abs(y2-y1);
	const xd = Math.abs(x2-x1);
	const a = Math.max(yd, xd);
	const b = Math.min(yd, xd);
return gcd(a,b) - 1;
	}