#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: linyuhang
	Language: C++
	Result: Accepted
	Time:19 ms
	Memory:2080 kb
****************************************************************/