高精度减法
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

const int N = 100000 + 10;

// 判断是否A >= B
bool cmp(vector<int> &A, vector<int> &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;
}

// C = A + B

vector<int> sub(vector<int> &a, vector<int> &b)
{
    vector<int> c;

    int t = 0;
    int i = 0;
    for (; i < b.size(); i++) 
    {
        if (a[i] >= b[i] + t) 
        {
            c.push_back(a[i] - b[i] - t);
            t = 0;
        }
        else 
        {
            c.push_back(a[i] - b[i] - t + 10);
            t = 1; 
        }
    }
    for (i; i < a.size(); i ++) 
    {
        if(a[i] >= t) 
        {
            c.push_back(a[i] - t);
            t = 0;
        }
        else 
        {
            c.push_back(a[i] + 10 - t); 
            t = 1;
        }
    }

    while (c.size() > 1 && c.back() == 0) c.pop_back();
    return c;
}
/*
vector<int> sub(vector<int> &A, vector<int> &B)
{
    vector<int> C;
    for (int i = 0, t = 0; i < A.size(); i ++)
    {
        int a = A[i] - t;
        if (i < B.size()) a -= B[i];
        C.push_back((a + 10) % 10);
        if (a < 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;
    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 (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;
}