n = int(input())
s = input()
res = 0
a = set()
for c in s:
if 'A' <= c <= 'Z':
res = max(res, len(a))
a.clear()
else:
a.add(c)
res = max(len(a), res)
print(res)
1302. Deepest Leaves Sum | 1209. Remove All Adjacent Duplicates in String II |
994. Rotting Oranges | 983. Minimum Cost For Tickets |
973. K Closest Points to Origin | 969. Pancake Sorting |
967. Numbers With Same Consecutive Differences | 957. Prison Cells After N Days |
946. Validate Stack Sequences | 921. Minimum Add to Make Parentheses Valid |
881. Boats to Save People | 497. Random Point in Non-overlapping Rectangles |
528. Random Pick with Weight | 470. Implement Rand10() Using Rand7() |
866. Prime Palindrome | 1516A - Tit for Tat |
622. Design Circular Queue | 814. Binary Tree Pruning |
791. Custom Sort String | 787. Cheapest Flights Within K Stops |
779. K-th Symbol in Grammar | 701. Insert into a Binary Search Tree |
429. N-ary Tree Level Order Traversal | 739. Daily Temperatures |
647. Palindromic Substrings | 583. Delete Operation for Two Strings |
518. Coin Change 2 | 516. Longest Palindromic Subsequence |
468. Validate IP Address | 450. Delete Node in a BST |