def connect(s, d):
    for i in range(len(s) - len(d), len(s)):
        if s[i:] == d[:len(s) - i]:
            return s[:i] + d[:]
            break
    else:
        return s[:] + d[:]
n = ""
for i in range(10):
    for j in range(10):
        for k in range(10):
            for l in range(10):
                n=connect(n,str(i) + str(j) + str(k) + str(l))
print(n)