N = int(input())
A = list(map(int, input().split()))

def rec(X, digit):
    if digit == -1:
        return 0
    X0, X1 = [], []
    for x in X:
        if x >> digit & 1:
            X1.append(x ^ (1 << digit))
        else:
            X0.append(x)
    if X0 and X1:
        return (1 << digit) + min(rec(X0, digit - 1), rec(X1, digit - 1))
    else:
        return rec(X, digit - 1)

print(rec(A, 30))