1 /************************************************************** 2     Problem: 2789 3     User: rausen 4     Language: C++ 5     Result: Accepted 6     Time:1060 ms 7     Memory:8704 kb 8 ****************************************************************/ 9  10 #include <cstdio>11 #include <cstring>12 #include <queue>13  14 #define lowbit(x) x & -x15 using namespace std;16 const int N = 1000005;17 int n;18 int val, BIT[N];19 long long ans;20 queue <int> q[26];21  22 int read() {23     char ch = getchar();24     while (ch < ‘A‘ || ‘Z‘ < ch)25         ch = getchar();26     return ch - ‘A‘;27 }28  29 void add(int x) {30     while (x <= n)31         ++BIT[x], x += lowbit(x);32 }33  34 int query(int x) {35     int res = 0;36     while (x)37         res += BIT[x], x -= lowbit(x);38     return res;39 }40  41 int main() {42     scanf("%d", &n);43     int i, t;44     for (i = 1; i <= n; ++i)45         q[t = read()].push(i);46     for (i = 1; i <= n; ++i) {47         t = read();48         val = q[t].front();49         q[t].pop();50         ans += query(n) - query(val);51         add(val);52     }53     printf("%lld\n", ans);54     return 0;55 }