#include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() using ll = long long; constexpr int INF = 0x3f3f3f3f; constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL; constexpr double EPS = 1e-8; constexpr int MOD = 998244353; // constexpr int MOD = 1000000007; constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1}; constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}; constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1}; template inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; } template inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; } struct IOSetup { IOSetup() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << fixed << setprecision(20); } } iosetup; struct Manacher { template explicit Manacher(const T& s) { T str; int n = s.size(); str.reserve(n * 2 + 1); for (int i = 0; i < n; ++i) { str.push_back(s[i]); str.push_back('$'); } str.pop_back(); n = str.size(); radius.resize(n); for (int i = 0, j = 1; i < n;) { while (i - j >= 0 && i + j < n && str[i - j] == str[i + j]) ++j; radius[i] = j; int k = 1; for (; i - k >= 0 && i + k < n && k + radius[i - k] < j; ++k) { radius[i + k] = radius[i - k]; } i += k; j -= k; } } int odd(const int idx) const { return (radius[idx * 2] + 1) / 2; } int even(const int idx) const { return radius[idx * 2 + 1] / 2; } bool is_palindrome(const int left, const int right) const { const int mid = (left + right - 1) / 2; return ((right - left) & 1 ? odd(mid) * 2 - 1 : even(mid) * 2) >= right - left; } private: std::vector radius; }; int main() { string a; cin >> a; const int n = a.length(); Manacher manacher(a); REP(i, n) { if (manacher.is_palindrome(i, n)) { string b = a.substr(0, i); ranges::reverse(b); a += b; break; } } cout << a << '\n'; return 0; }