#include<bits/stdc++.h>
using namespace std;
int a[11111110],b[1111110],c[11111110];
int main()
{
    string s1,s2;cin>>s1>>s2;
    reverse(s1.begin(),s1.end());
    reverse(s2.begin(),s2.end());
    int lena=s1.size(),lenb=s2.size(),lenc=max(lena,lenb)+1;
    for(int i=0;i<lena;i++)
    {
        a[i]=s1[i]-'0';
    }
    for(int i=0;i<lenb;i++)
    {
        b[i]=s2[i]-'0';
    }
    for(int i=0,t=0;i<=lenc;i++)
    {
        if(a[i]<b[i])
        {
            a[i]+=10;
            a[i+1]-=1;
        }
        c[i]=a[i]-b[i];
        c[i]=c[i]%10;
    }
    while(lenc&&c[lenc]==0) lenc--;
    for(int i=lenc;i>=0;i--)
    {
        cout<<c[i];
    }
    return 0;
}