#include <bits/stdc++.h>
char str[int(1e5) + 7];
int main() {
    std::cin >> str;
    std::string ans = "";
    int len = int(strlen(str)), l = 0, r = len - 1;
    bool flag = !bool(len & 1);
    while (l <= r) {
        if (flag) ans = str[r--] + ans;
        else ans = str[l++] + ans;
        flag = !flag;
    }
    std::cout << ans << std::endl;
    return 0;
}