题目传送门
1 /*
2 模拟：这就是一道模拟水题，看到标签是贪心，还以为错了呢
3 题目倒是很长:)
4 */
5 #include <cstdio>
6 #include <algorithm>
7 #include <iostream>
8 #include <algorithm>
9 #include <cstring>
10 using namespace std;
11
12 const int MAXN = 2e5 + 10;
13 const int INF = 0x3f3f3f3f;
14 int cnt[33];
15 char s[MAXN];
16
17 int main(void) //Codeforces Round #297 (Div. 2) A. Vitaliy and Pie
18 {
19 int n;
20 while (scanf ("%d", &n) == 1)
21 {
22 scanf ("%s", s); int len = strlen (s);
23 memset (cnt, 0, sizeof (cnt));
24
25 int ans = 0;
26 for (int i=1; i<len; i+=2)
27 {
28 cnt[s[i-1]-'a']++;
29 if (cnt[s[i]-'A']) cnt[s[i]-'A']--;
30 else ans++;
31 }
32
33 printf ("%d
", ans);
34 }
35
36 return 0;
37 }
38
39
40 /*
41 3
42 aAbB
43 4
44 aBaCaB
45 5
46 xYyXzZaZ
47 */