解

#include<bits/stdc++.h>
using namespace std;
int main(){
	string a,b,tmp;
	cin>>a>>b;
	if(b.size()>a.size() || (a.size()==b.size() && b>a)){
		tmp=a;
		a=b;
		b=tmp;
		cout<<'-';
	}  
	int az=a.size();
	int bz=b.size();
	int abz=max(az,bz);
	int ar[abz];
	ar[abz-1]=0;
    for(int i=0;i<abz;i++)
    {
        int aa=0,bb=0;
        if(i<az)
        aa=a[az-i-1] - '0';
        if(i<bz)
        bb=b[bz-i-1] - '0';
        ar[i]=aa-bb;
    }
    for(int i=0;i<abz;i++)
    {
        if(ar[i]>=10)
        {
        ar[i+1]+=ar[i]/10;
        ar[i]+=10;
        }
    }
    bool ok = false;
	for(int i=abz-1; i>=0; i--)	
    {
    	if(not ok && ar[i] != 0)
    		ok = true;
    	if(ok)
    		cout << ar[i];
	}

	return 0;	
}