AC

#include <bits/stdc++.h>
using namespace std;

string fun(string a, string b){
	string res = "";
	
	if (a.size() < b.size() || a.size() == b.size() && a < b){
		swap(a, b);
		res += '-';
	}
	
	int la = a.size(), lb = b.size();
	vector<int> A(la+10), B(la+10), C(la+10);
	for (int i=0;i<la;i++) A[i] = a[la-i-1]-'0';
	for (int i=0;i<lb;i++) B[i] = b[lb-i-1]-'0';
	
	for (int i = 0; i < la; i++){
		C[i] += A[i] - B[i];
		if (C[i] < 0){ 
			C[i+1]--;
			C[i]+=10; 
		}
	}
	
	int len = la-1;
	while (C[len]==0&&len>0) len--; 
	
	for (int i=len;i>=0;i--){
		res += C[i]+'0';
	}
	return res;
}

int main(){
	string a, b;
	cin >> a >> b;
	cout << fun(a, b); 
	return 0;
}

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