n = int(input())
a = list(map(int, input().split()))
def dfs(a, i):
    if i < 0:
        return 0
    x = []
    y = []
    for j in a:
        if j&(1<<i) == 0:
            x.append(j)
        else:
            y.append(j)
    if not x:
        return dfs(y, i-1)
    elif not y:
        return dfs(x, i-1)
    return (1<<i) + min(dfs(x, i-1), dfs(y, i-1))
print(dfs(a, 30))