by hansang:

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1e5+10;
struct node{LL s, e;} a[N];
bool cmp(node n1, node n2){
	if(n1.s!=n2.s) return n1.s<n2.s;
	else return (n1.e-n1.s)<(n2.e-n2.s);
}
LL calc(node no){
	return (no.e-no.s)*(no.e-no.s);
}
int main(){
	int n; scanf("%d", &n);
	for(int i=1; i<=n; i++) scanf("%lld%lld", &a[i].s, &a[i].e);
	sort(a+1, a+n+1, cmp);
	LL ans=0; ans+=calc(a[1]); int t=1;
	for(int i=2; i<=n; i++){
		if(a[i].e<=a[t].e) continue;
		if(a[t].e<=a[i].s) ans+=calc(a[i]), t=i;
		else ans+=calc(a[i])-calc({a[i].s, a[t].e}), t=i;
	}
	printf("%lld\n", ans);
	return 0;
}

by hansang:

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1e5+10;
struct node{LL s, e;} a[N];
bool cmp(node n1, node n2){
if(n1.s!=n2.s) return n1.s<n2.s;
else return (n1.e-n1.s)<(n2.e-n2.s);
}
LL calc(node no){
return (no.e-no.s)*(no.e-no.s);
}
int main(){
int n; scanf("%d", &n);
for(int i=1; i<=n; i++) scanf("%lld%lld", &a[i].s, &a[i].e);
sort(a+1, a+n+1, cmp);
LL ans=0; ans+=calc(a[1]); int t=1;
for(int i=2; i<=n; i++){
if(a[i].e<=a[t].e) continue;
if(a[t].e<=a[i].s) ans+=calc(a[i]), t=i;
else ans+=calc(a[i])-calc({a[i].s, a[t].e}), t=i;
}
printf("%lld\n", ans);
return 0;
}