#include <bits/stdc++.h>
#define FIXED_FLOAT(x) std::fixed <<std::setprecision(20) << (x)
#define all(v) (v).begin(), (v).end()
using namespace std;
#define forn(i,n) for (int i = 0; i < (n); ++i)
#define rforn(i, n) for(int i = (n) - 1;i >= 0;--i)
#define sz(x) (int)x.size()
using ll = long long;
int mod = (ll)1e9 + 7;
#define PI acos(-1)
typedef pair<int, int> pairs;
const int INF = 1e9 + 1;
const int N = 2e5 + 100;
const double eps = 1e-7;
template <class T> using V = vector<T>;
template <class T> using VV = V<V<T>>;
template<class T, size_t SZ> using AR = array<T, SZ>;
template<class T> using PR = pair<T, T>;
template <typename XPAX>
bool ckma(XPAX &x, XPAX y) {
return (x < y ? x = y, 1 : 0);
}
template <typename XPAX>
bool ckmi(XPAX &x, XPAX y) {
return (x > y ? x = y, 1 : 0);
}
int A[N], B[N];
void add(ll &x, ll y) {
x += y;
if(x >= mod)x -= mod;
}
void solve() {
int n;
cin >> n;
forn(i, n) cin >> A[i] >> B[i];
VV<ll> dp(n);
forn(i, n) dp[i].push_back(0);
for(int i = 0;i < n;++i) {
for(int x = A[i];x <= B[i];++x) {
ll now = 1;
for(int j = 0;j < i;++j) {
if(A[j] < x)
add(now, dp[j][min(B[j] - A[j] + 1, x - A[j])]);
}
dp[i].push_back((dp[i].back() + now) % mod);
}
}
ll ret = 0;
forn(i, n) add(ret, dp[i].back());
cout << ret << '\n';
}
void test_case() {
int t;
cin >> t;
forn(p, t) {
//cout << "Case #" << p + 1 << ": ";
solve();
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
solve();
}
