#include <bits/stdc++.h>
using namespace std;
int main() {
    int n, a, b, c, d, r, i;
    cin >> n;
    a = n / 1000;      
    b = (n / 100) % 10; 
    c = (n / 10) % 10;  
    d = n % 10;
    r = d * 1000 + c * 100 + b * 10 + a;
    i = n - r;
    cout << i << endl;
    return 0;
}
/**************************************************************
	Problem: 1702
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/