//uva10407 #include <cstdio> #include <iostream> using namespace std; int ABS(int x) { return x < 0 ? -x : x; } int GCD(int a, int b) { return b == 0 ? a : GCD(b, a%b); } int main(void) { int num[1005], ans, i, j, n; while(scanf("%d", &num[0]) && num[0]) { n = 1; ans = 0; while(scanf("%d", &num[n]) && num[n]) ++n; for(i = 0; i < n; ++i) for(j = i + 1; j < n; ++j) if(num[i] - num[j] != 0) ans = GCD(ABS(num[i] - num[j]), ans); printf("%d\n", ans); } return 0; }