大重载照亮世界，int128没有输入那就给他写个输入（其实和函数一样）

#include<bits/stdc++.h>
using namespace std;
__int128 a,b,l,g,ans;
istream&operator>>(istream &is,__int128 &n){
	string s;
	is>>s;
	n=0;
	for(char i:s) n=n*10+i-'0';
	return is;
}
ostream&operator<<(ostream &is,__int128 &n){
	string s;
	while(n){
		s+='0'+n%10;
		n/=10;
	}
	reverse(s.begin(),s.end());
	return is<<s;
}
__int128 gcd(__int128 a,__int128 b){
	return a%b==0?b:gcd(b,a%b);
}
int main(){
	freopen("easy.in","r",stdin);
	freopen("easy.out","w",stdout);
	cin>>a>>b;
	g=gcd(a,b);
	l=a/gcd(a,b)*b;
	ans=g^l;
	cout<<ans<<endl;
	return 0;
}

难点在于 __int128 需要快读快写。

#include<bits/stdc++.h>
using namespace std;
__int128 read(){
	__int128 flag=1,num=0;
	char cum=getchar();
	while(cum<'0'||cum>'9'){
		if(cum=='-') flag=-1;
		cum=getchar();
	}
	while(cum>='0'&&cum<='9'){
		num=(num<<3)+(num<<1)+(cum-'0');
		cum=getchar();
	}
	return flag*num;
}
void write(__int128 sum){
	if(sum>=10){
		write(sum/10);
		printf("%d",(int)(sum%10));
	}
	else printf("%d",(int)sum);
}
__int128 gcd(__int128 a,__int128 b){
	return a%b==0?b:gcd(b,a%b);
}
int main(){
	freopen("easy.in","r",stdin);
	freopen("easy.out","w",stdout);
	__int128 a=read(),b=read();
	__int128 g=gcd(a,b),l=a/gcd(a,b)*b;
	__int128 ans=g^l;
	write(ans);
	return 0;
}