啊这……10pts
样例测了是0,输入输不进去!!!
#include<bits/stdc++.h>
using namespace std;
int a[20000],b[20000],n,ans;
int main(){
scanf("%d",&n);
for(int i = 0; i < n; i++) scanf("%d%d",&a[i],&b[i]);
sort(a,a + n);
sort(b,b + n);
for(int i = 0; i < n; i++){
ans += b[i] - a[i];
if(i - 1 < n && b[i] > a[i + 1]) ans -= b[i] - a[i + 1];
}
printf("%d",ans);
return 0;
}