#include <iostream>
#include <cmath>
using namespace std;

int main() 
{
    int a, b, c,d,e,x;
    cin >> a;
    if (a < 999 || a > 10000)
        cout << "no u";
    else {b = a/1000;
    c = a/100%10;
    d =a/10%10;
    e=a%10;
    x = (e*1000)+d*100+c*10+b;}
    cout << x;
}