#include <bits/stdc++.h> 
using namespace std;
long long jian(string a,string b){
	while(b.size()<a.size()) b="0"+b;
	int cnt=0;
	string s=""; 
	for(int i=a.size()-1;i>=0;i--){
		int x=(a[i]-'0')-(b[i]-'0')-cnt;
		if(x<0){
			x+=10;
			cnt=1;
		}else{
			cnt=0;
		}
		char ch=x+'0';
		s=ch+s;
	}
	long long num=0;
	for(char c:s){
		int x=c-'0';
		num=num*10+x;
	}
	return num;
}
string liu(string a,string b){
	long long s=jian(a,b);
	if(s==0){
		return "0";
	}
	string m="";
	const string z="0123456789ABCDEF";
	while(s>0){
		m=z[s%16]+m;
		s/=16;
	}
	return m;
}
int main(){
	string a,b;
	cin>>a>>b;
	if(a<b) swap(a,b);
	cout<<liu(a,b);
	return 0; 
}