import sys
sys.setrecursionlimit(10**6)

def dfs(d, group):
    if d==L:
        return 0
        
    zero_group, one_group = [], []
    
    for b in group:
        if b[d]=='0':
            zero_group.append(b)
        else:
            one_group.append(b)
    
    if len(zero_group)==0:
        return dfs(d+1, one_group)
    elif len(one_group)==0:
        return dfs(d+1, zero_group)
    else:
        return min(dfs(d+1, zero_group)+2**(L-d-1), dfs(d+1, one_group)+2**(L-d-1))

N = int(input())
a = list(map(int, input().split()))
a = [format(ai, 'b') for ai in a]
L = max(len(ai) for ai in a)
a = ['0'*(L-len(ai))+ai for ai in a]

print(dfs(0, a))