#include <bits/stdc++.h>
#define FASTIO
using namespace std;

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
        auto operator()(const Args&... args) const -> decltype((std::cout << ... << std::declval<Args>()), void()) { print(args...); }
        template <typename T>
        auto pvec(const T& vec, size_t sz) const -> decltype(std::cout << std::declval<decltype(std::declval<T>()[0])>(), void()) {
            for (size_t i = 0; i < sz; i++)
                std::cout << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
        auto pmat(const T& mat, size_t h, size_t w) -> decltype(std::cout << std::declval<decltype(std::declval<T>()[0][0])>(), void()) {
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    std::cout << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { std::cout << term; }
        void print_rest() const { std::cout << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { std::cout << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { std::cout << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints prints;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void solve() {
    int N;
    cin >> N;
    ll ans = 0;
    for (ll i = 0; i < N; i++) {
        ll a, b;
        cin >> a >> b;
        ans += (a + b) * (b - a + 1) / 2;
    }
    prints()(ans);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}
#include<bits/stdc++.h>
using namespace std;
#define int long long int
#define vi vector<int>
#define pb push_back
#define ff first
#define ss second
#define ppi pair<int,int>
#define forn(i,n) for(int i=0;i<n;i++)
#define M 1000000007
#define all(x) x.begin(), x.end()
#define fastio ios_base::sync_with_stdio(false);cin.tie(0)

int ps[1000007];

void solve() {

	int n;
	cin >> n;
	vi v;
	for (int i = 1; i < 1000007; i++) {
		v.pb(i);
	}


	ps[0] = v[0];
	for (int i = 1; i < 1000001; i++) {
		ps[i] = ps[i - 1] + v[i];
	}
	int ans = 0;
	while (n--) {
		int x, y;
		cin >> x >> y;
		int t = x;
		x--;
		y--;
		ans += (t + (ps[y] - ps[x]));
		// cout << ans << endl;
	}

	cout << ans << endl;



}


int32_t main() {

	fastio;

#ifndef ONLINE_JUDGE
	freopen("input1.txt", "r", stdin);
	freopen("output1.txt", "w", stdout);
#endif



	solve();





	return 0;
}