def g(s):
    d=set()
    for i in s:
        if i not in d: d.add(i)
    return len(d)
x=[]    
for _ in range(int(input())):
    n=input().replace("\r","")
    x.append((n,g(n)))
x.sort(key=lambda x: (x[1],x[0]))
print(x[0][0])