UVa 10407

#include<bits/stdc++.h>
using namespace std;

typedef unsigned long long int  ull;
typedef long long int      ll;
typedef vector<int>        vi;
typedef vector<ll>         vll;
typedef vector<vi>         vvi;
typedef pair<int,int >     pii;
typedef vector< pii >      vpii;
typedef set<int>           sti;

#define sc                 scanf
#define pf                 printf
#define sci(n)             scanf("%d",&n)
#define scl(n)             scanf("%lld",&n)
#define scd(n)             scanf("%lf",&n)
#define scs(s)             scanf("%s",s)
#define pfi(n)             printf("%d",n)
#define pfl(n)             printf("%lld",n)
#define pff(n)             cout<<n
#define line               printf("\n")
#define spc                printf(" ")
#define loop(i,x,y)        for(int i=int(x); i<=int(y); i++)
#define rloop(i,y,x)       for(int i=int(y); i>=int(x); i--)
#define cspf(i)            printf("Case %d: ", i)
#define pb                 push_back
#define mp                 make_pair
#define ff                 first
#define ss                 second
#define all(v)             v.begin(),v.end()
#define rall(v)            v.rbegin(),v.rend()
#define read()             freopen("input.txt", "r", stdin)
#define write()            freopen("output.txt", "w", stdout)
/// Constants
#define eps                1e-9
#define PI                 acos(-1.0)  // 3.1415926535897932
#define MAX                1000007


int main(){
    //read();
   // write();
    //ios_base::sync_with_stdio(false);
    //cin.tie(NULL);
    int n;
    while(cin>>n && n){
        vi vt;
        vt.pb(n);
        while(cin>>n && n){
            vt.pb(n);
        }
        int k=abs(vt[0]-vt[1]);
        for(int i=2;i<vt.size();i++){
            k=__gcd(k,abs(vt[i]-vt[i-1]));
        }
        cout<<k;
        line;
    }
    return 0;
}