CodeForces Round #301 Div.2

#include <cstdio>
#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;

typedef long long LL;
const int maxn = 200000 + 10;

int a[maxn], b[maxn], x[maxn], r[maxn];
LL sum[maxn], s[maxn];
int n, m;

inline int lowbit(int x) { return x&(-x); }

void add(int x, LL d)
{ while(x <= m) { s[x] += d; x += lowbit(x); } }

LL query(int x)
{
LL ans = 0;
while(x) { ans += s[x]; x -= lowbit(x); }
return ans;
}

int main()
{
//freopen("in.txt", "r", stdin);

cin >> n;
for(int i = 1; i <= n; i++)
{
scanf("%d%d", &a[i], &b[i]);
x[i*2-1] = a[i]; x[i*2] = b[i];
}
sort(x + 1, x + 1 + n*2);
m = unique(x + 1, x + 1 + n*2) - x - 1;
for(int i = 1; i <= m; i++)
{
sum[i] = sum[i - 1] + x[i] - x[i - 1] - 1;
r[i] = i;
}
for(int i = 1; i <= n; i++)
{
int ta = lower_bound(x + 1, x + 1 + m, a[i]) - x;
int tb = lower_bound(x + 1, x + 1 + m, b[i]) - x;
swap(r[ta], r[tb]);
}

LL inv = 0;
for(int i = m; i > 0; i--)
{
inv += query(r[i]);
add(r[i], 1);
inv += abs(sum[i] - sum[r[i]]);
}

cout << inv << endl;

return 0;
}