codeforeces 540E(树状数组

#include<iostream>
#include<map>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<queue>
#include<stack>
#include<functional>
#include<set>
#define pb push_back
#define fs first
#define se second
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
const int maxv=1e5*4;
struct BIT{
    ll a[maxv];
    void add(int p,int x){
        while(p<maxv){
            a[p]+=x;
            p+=p&-p;
        }
    }
    ll sum(int p){
        ll ans=0;
        while(p>0){
            ans+=a[p];
            p-=p&-p;
        }
        return ans;
    }
    ll after(int a){
        return sum(maxv-1)-sum(a);
    }
}B;
int a[maxv];
int b[maxv];
int c[maxv];
int mid[maxv];
int sq[maxv];
int n;
map<int,int> mii;
int main(){
    freopen("/home/files/CppFiles/in","r",stdin);
    cin>>n;
    for(int i=0;i<n;i++){
        scanf("%d%d",a+i,b+i);
        c[i*2]=a[i];
        c[i*2+1]=b[i];
    }
    sort(c,c+2*n);
    int h=unique(c,c+2*n)-c;
    for(int i=1;i<h;i++){
        mid[i]=c[i]-c[i-1]-1;
    }
    for(int i=0;i<h;i++){
        mii[c[i]]=i+1;
    }
    for(int i=0;i<maxv;i++){
        sq[i]=i;
    }
    for(int i=0;i<n;i++){
        swap(sq[mii[a[i]]],sq[mii[b[i]]]);
    }
    ll ans=0;
    for(int i=1;i<=h;i++){
        ll now=sq[i];
        ans+=B.after(now*2-1);
        B.add(now*2-1,1);
        ans+=mid[i]*B.after(i*2);
        B.add(2*i,mid[i]);
    }
    cout<<ans<<endl;
    return 0;
}