UVa 10407 - Simple division

// UVa 10407 - Simple division

#include <iostream>
#include <stdio.h>
#include <vector>
#include <algorithm>
using namespace std;

int gcd(int a, int b) {
	if (a == 0)
		return b;
	else
		return gcd(b % a, a);
}

int main() {
	int a;
	cin >> a;
	while (a) {
		// input
		vector<int> v;
		do {
			v.push_back(a);
			cin >> a;
		} while (a);
		// prepare
		unique(v.begin(), v.end());
		// gen d
		vector<int> d;
		for (int i = 1; i < v.size(); i++)
			d.push_back(v[i] - v[i - 1]);
		// gcd
		int g = abs(d[0]);
		for (int i = 1; i < d.size(); i++)
			g = gcd(g, abs(d[i]));
		cout << g << endl;
		cin >> a;
	}

	return 0;
}