#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cstdio>
#include<windows.h>
using namespace std;
#define SIZE 1000
int main1() {string s1, s2 , res;    cin >> s1 >> s2;int len1 = s1.size();int len2 = s2.size();reverse(s1.begin(),s1.end());reverse(s2.begin(), s2.end());//plusint len = min(len1, len2);int flag = 0;//进位int num1, num2,num3;for (int i = 0; i < len; ++i) {num1 = s1[i] - '0';//string to intnum2 = s2[i] - '0';num3 = num1 + num2 + flag;if (num3 > 9) {flag = 1;num3 = num3 % 10;}else {flag = 0;}res.push_back(num3 + '0');}//find max len1 or len2if (len1 == len) {for (int i = len; i < len2; ++i) {num2 = s2[i] - '0';num3 = num2 + flag;if (num3 > 9) {flag = 1;num3 = num3 % 10;}else {flag = 0;}res.push_back(num3 + '0');}}if (len2 == len) {for (int i = len; i < len1; ++i) {num1 = s1[i] - '0';num3 = num1 + flag;if (num3 > 9) {flag = 1;num3 = num3 % 10;}else {flag = 0;}res.push_back(num3 + '0');}}if (len1 == len2 && flag == 1) {res.push_back(flag + '0');}reverse(res.begin(), res.end());cout << res << endl;return 0;
}

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
string sub1(string s1, string s2) {reverse(s1.begin(),s1.end());reverse(s2.begin(), s2.end());int len1 = s1.size();int len2 = s2.size();for (int i = 0; i < len2; ++i) {if (s1[i] >= s2[i]) {s1[i] = s1[i] - s2[i] + '0';}else {//需要借位s1[i] = 10 + s1[i] - s2[i] + '0';s1[i + 1] = s1[i + 1] - 1;//这里为什么不加上'0',因为前面加上'0'的本质是s1[i] - s2[i]，//只有加上0这个字符的ASCII码才能获得对应的数字比如相减等于16，//加上0的ASCII码，得到字符16
        }                }cout << s1 << endl;for (int j = len2; j < len1; ++j) {if (s1[j] - '0' >= 0) {reverse(s1.begin(), s1.end());return s1;}else {s1[j] = 10 + s1[j];s1[j + 1] = s1[j + 1] - 1 ;}}reverse(s1.begin(), s1.end());return s1;
}
int main() {string s1, s2, res;cin >> s1 >> s2;//保证s1 > s2if (s1.size() < s2.size() || s1.size() == s2.size() && s1 < s2) {swap(s1, s2);}res = sub1(s1, s2);//cout << res << endl;int pos = res.find_first_not_of('0');res = res.substr(pos);cout << res << endl;system("pause");return 0;}