91巨献样例没过AC了题目？？？

#include<bits/stdc++.h>
#define int long long
#define PII pair<int,int>
#define fir first
#define sec second
#define pc putchar
using namespace std;
namespace IO{
	inline int rd(){
		int x=0,f=1;
		char c=getchar();
		while(c<'0'||c>'9'){
			if(c=='-'){
				f=-1;
			}
			c=getchar();
		}
		while(c>='0'&&c<='9'){
			x=(x<<1)+(x<<3)+(c^48);
			c=getchar();
		}
		return x*f;
	}
	inline void wt(int x){
		if(x<0){
			x=-x;
			putchar('-');
		}
		if(x>9){
			wt(x/10),putchar(x%10+'0');
		}
		else{
			putchar(x+'0');
		}
		return ;
	}
}
using namespace IO;
namespace Main{
	const int N=2e4+7;
	int n,res;
	int l[N],r[N];
	inline void main(){
		n=rd();
		for(int i=1;i<=n;i++){
			l[i]=rd(),r[i]=rd();
		}
		sort(l+1,l+n+1),sort(r+1,r+n+1);
		for(int i=1;i<=n;i++){
			res+=r[i]-l[i];
			if(r[i-1]>l[i]){
				res-=r[i-1]-l[i];
			}
		}
		wt(res);
		return ;
	}
}
signed main(){
	Main::main();
	return 0;
}
/*
3
-1 1
5 11
2 9

2
0 2870
0 4486
*/