#include<iostream>
using namespace std;
int main(){
	int a,b,c,d,e,n;
	cin>>n;
	a=n/1000;
	b=n/100%10;
	c=n/10%10;
	d=n%10;
	e=d*1000+c*100+b*10+a;
	n=n-e;
	cout<<n;
}
/**************************************************************
	Problem: 1702
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/