Codeforces 525A Vitaliy and Pie

 1 // File Name: a.cpp
 2 // Author: darkdream
 3 // Created Time: 2015年03月27日 星期五 00时44分21秒
 4 
 5 #include<vector>
 6 #include<list>
 7 #include<map>
 8 #include<set>
 9 #include<deque>
10 #include<stack>
11 #include<bitset>
12 #include<algorithm>
13 #include<functional>
14 #include<numeric>
15 #include<utility>
16 #include<sstream>
17 #include<iostream>
18 #include<iomanip>
19 #include<cstdio>
20 #include<cmath>
21 #include<cstdlib>
22 #include<cstring>
23 #include<ctime>
24 #define LL long long
25 
26 using namespace std;
27 char str[1000005];
28 int hs[1000];
29 int main(){
30    int n ;
31    scanf("%d",&n);
32    scanf("%s",&str[1]);
33    int sum = 0; 
34    for(int i = 1;i <= 2*n-2;i ++ )
35    {
36        if(str[i] <= ‘z‘ && str[i] >= ‘a‘) 
37        {
38          hs[str[i] -‘a‘] ++ ;
39        }else{
40          if(hs[str[i]-‘A‘] == 0 )
41              sum ++;
42          else hs[str[i]-‘A‘] -- ; 
43        }
44    }
45    printf("%d\n",sum);
46 return 0;
47 }