#include <iostream>
#include <vector>

using namespace std;

//可以比较字符串，也可以比较vector
bool cmpString(string &a, string &b)//是否 a >= b
{
    if (a.size() != b.size()) return a.size() > b.size();
    for (int i = 0; i < a.size(); i ++ )
        if (a[i] != b[i]) return a[i] > b[i];
    return true; // a == b;
}
bool cmpVector(vector<int> &A, vector<int> &B)// 是否 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; // A == B
}
vector<int> sub(vector<int> &A, vector<int> &B)
{
    vector<int> C;

    int t = 0;//需要一个为零的借位
    for (int i = 0; i < A.size(); i ++ )
    {
        t = A[i] - t;
        if (i < B.size()) t -= B[i];
        C.push_back((t + 10)%10); //t >= 0, t->t ; t < 0,t -> t + 10;
        if (t < 0) t = 1; // 已经借位
        else t = 0; // 没借位
    }
    while (C.size() > 1 && C.back() == 0) C.pop_back(); // 除掉高位的零，且保证C至少保留一位
    return C;
}
int main()
{
    string a, b; // 保证都是正整数
    vector<int> A, B;

    cin >> a >> b;
    for (int i = a.size() - 1; i >= 0; i -- ) A.push_back(a[i] - '0');
    for (int i = b.size() - 1; i >= 0; i -- ) B.push_back(b[i] - '0');

    if (cmpVector(A, B))//A >= B A - B 
    {
        auto C = sub(A, B);
        for (int i = C.size() - 1; i >= 0; i -- ) printf("%d", C[i]);
    }
    else//A < B - (B - A)
    {
        printf("-");
        auto C = sub(B, A);
        for (int i = C.size() - 1; i >= 0; i -- ) printf("%d", C[i]);
    }
    return 0;
}