#include <iostream>
#include <vector>
using namespace std;
bool cmp(vector<int> &A,vector<int> &B)  //判断是否有A>=B
{
    if(A.size()!=B.size())
        return A.size()>B.size();
    for(int i=A.size()-1;i>=0;i--)
        if(A[i]!=B[i])
            return A[i]>B[i];
    return true;
}

vector<int> sub(vector<int> &A,vector<int> &B)  //C=A-B
{
    vector<int> C;
    for(int i=0,t=0;i<A.size();i++)
    {
        t=A[i]-t;
        if(i<B.size())
            t-=B[i];
        C.push_back((t+10)%10);
        if(t<0)
            t=1;
        else
            t=0;
    }
    while(C.size()>1&&C.back()==0)
        C.pop_back();
    return C;
}
int main()
{
    string a,b;
    vector<int> A,B;
    cin>>a>>b;   //a="123456"
    for(int i=a.size()-1;i>=0;i--)
        A.push_back(a[i]-'0');    //A=[6,5,4,3,2,1]
    for(int i=b.size()-1;i>=0;i--)
        B.push_back(b[i]-'0');
    if(cmp(A,B))
    {
        auto C=sub(A,B);
        for(int i=C.size()-1;i>=0;i--)
            printf("%d",C[i]);
    }
    else
    {
        auto C=sub(B,A);
        printf("-");
        for(int i=C.size()-1;i>=0;i--)
            printf("%d",C[i]);
    }
    return 0;
}