#include <bits/stdc++.h>

using namespace std;

int main() {
    //输入+输出重定向
    //freopen("../x.in", "r", stdin);
    //freopen("../x.out", "w", stdout);
    string s;
    cin >> s;
    stack<int> Stack;
    for (int i = 0; i < s.size() / 2; ++i) {
        Stack.push(s[i]);
    }
    bool isHuiWen = true;
    for (int i = s.size() / 2 + 1; i < s.size(); ++i) {
        char c = Stack.top();
        Stack.pop();
        if (s[i] != c) {
            isHuiWen = false;
            break;
        }
    }
    if (isHuiWen)cout << "yes" << endl;
    else cout << "no" << endl;

    //关闭文件
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}