文章标题

#include<iostream>#include<string>using namespace std;int main(){    string s;    string::iterator itb, it;    int len, ans = 0, i, j;    int b = 0;    cin >> len >> s;    itb = s.begin();    it = s.end() - 1;    if(len > 1)    while (true) {        if (it != itb && *itb != *it)            --it;        else if (it == itb) {            if(len % 2 != 1 || b == 1) {                b = 2;                break;            }            char x = *it;            s.erase(it);            s.insert(itb + s.size() / 2, x);            ans += s.size() / 2;            b = 1;            it = s.end() - 1;        }        else {            ans += s.end() - it - 1;            s.erase(it);            s.erase(itb);            if (s.size() < 2)                break;            it = s.end() - 1;        }    }    if (b != 2)        cout << ans;    else        cout << "Impossible";    return 0;}