// -----------------------------------
// author   : MatsuTaku
// country  : Japan
// created  : 11/01/20 20:25:34
// -----------------------------------

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main() {
  cin.tie(nullptr); ios::sync_with_stdio(false);

  int n; cin>>n;
  ll ans = 0;
  for (int i = 0; i < n; i++) {
    ll a,b; cin>>a>>b;
    ans += b*(b+1)/2;
    ans -= (a-1)*a/2;
  }
  cout << ans << endl;

  return 0;
}

//#pragma GCC optimize ("O2")
//#pragma GCC target ("avx2")
//#include<bits/stdc++.h>
//#include<atcoder/all>

#include<cstdio>
#include<cstring>

//using namespace atcoder;
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Would
#define you
#define please

const int CM = 1 << 17, CL = 12;
char cn[CM + CL], * ci = cn + CM + CL, * owa = cn + CM, ct;
const ll ma0 = 1157442765409226768;
const ll ma1 = 1085102592571150095;
const ll ma2 = 71777214294589695;
const ll ma3 = 281470681808895;
const ll ma4 = 4294967295;
inline int getint() {
	if (ci - owa > 0) {
		memcpy(cn, owa, CL);
		ci -= CM;
		fread(cn + CL, 1, CM, stdin);
	}
	ll tmp = *(ll*)ci;
	int dig = 68 - __builtin_ctzll((tmp & ma0) ^ ma0);
	tmp = tmp << dig & ma1;
	tmp = tmp * 10 + (tmp >> 8) & ma2;
	tmp = tmp * 100 + (tmp >> 16) & ma3;
	tmp = tmp * 10000 + (tmp >> 32) & ma4;
	ci += 72 - dig >> 3;
	return tmp;
}

int main() {
	//cin.tie(0);
	//ios::sync_with_stdio(false);


	int N = getint();
	ll kotae = 0;

	rep(i, N) {
		int a = getint(), b = getint();
		kotae += ll(b - a + 1) * (b + a);
	}

	printf("%lld\n", kotae / 2);


	Would you please return 0;
}