#include<bits/stdc++.h>
using namespace std;
int a[250],b[250],c[250],p=0;
int main(){
	string s1,s2;
	cin>>s1>>s2;
	if(s1.size()<s2.size()||(s1.size()==s2.size()&&s1<s2)){
	cout<<'-';
	swap(s1,s2);
	}

	for(int i=s1.size()-1;i>=0;i--){
        a[s1.size()-1-i]=s1[i]-48;
    }
	for(int i=s2.size()-1;i>=0;i--){
        b[s2.size()-1-i]=s2[i]-48;
    }
    //验证是否倒序
//    for(int i=0;i<s1.size();i++) cout<<a[i];
//    cout<<endl;
//    for(int i=0;i<s2.size();i++) cout<<b[i];
	for(int i=0;i<s1.size();i++){
		if(a[i]<b[i]){
			a[i]=a[i]+10;
			a[i+1]=a[i+1]-1;
		}
		c[i]=a[i]-b[i];
	}
	for(int i=s1.size()-1;i>=0;i--){
		if(c[i]!=0){
			p=i;
			break;
		}
	}
//	for(int i=0;i<s1.size();i++) cout<<a[i]<<" ";
//	cout<<endl;

//	for(int i=0;i<s1.size();i++) cout<<c[i]<<" ";
	for(int i=p;i>=0;i--){
		cout<<c[i];
	}



















	return 0;
}

/**************************************************************
	Problem: 1269
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2080 kb
****************************************************************/