A+B problem

#include <bits/stdc++.h>
using namespace std;
typedef long long kun;
const int N=1e7;
string a,b;
int x[N],y[N],s[N],mx;
int main(){
	cin>>a>>b;
    int A=a.length(),B=b.length();
	for(int i=0;i<A;i++)x[i] = a[A-1-i]-'0';
	for(int i=0;i<B;i++)y[i] = b[B-1-i]-'0';
	mx=max(A,B)+1;
	for(int i=0;i<mx;i++){
		s[i]+=x[i]+y[i];
		if(s[i]>9){
			s[i+1]++;
			s[i]%=10;
		}
	}while(s[mx-1]==0&&mx>0)mx--;
	while(mx--)cout<<s[mx];
}