#include <cstdio>
#include <algorithm>
#include <vector>
//FILE *fin = fopen("a.in", "r"), *fout = fopen("a.out", "w");
#define fin stdin
#define fout stdout
#define MOD 1000000007
inline void precalcCombinari(std::vector < std::vector < int > > &comb) {
for (int i = 0; i < (int)comb.size(); i++) {
comb[i][0] = 1;
for (int j = 1; j <= i; j++)
comb[i][j] = (comb[i - 1][j] + comb[i - 1][j - 1]) % MOD;
}
}
inline bool getValues(int n, int a, int b, std::vector < int > &A, std::vector < int > &B, std::vector < bool > &avem) {
bool ans = 0;
for (int i = 1; i <= n; i++) {
avem[i] = A[i] <= a && B[i] >= b - 1;
ans |= avem[i];
}
return ans;
}
inline int lgput(int a, int n) {
int r = 1;
while (n) {
if (n % 2)
r = 1LL * r * a % MOD;
a = 1LL * a * a % MOD;
n /= 2;
}
return r;
}
inline void calcCombinari(std::vector < int > &comb, int n) {
comb[0] = 1;
for (int i = 1; i < (int)comb.size(); i++)
comb[i] = 1LL * comb[i - 1] * (n - i + 1) % MOD * lgput(i, MOD - 2) % MOD;
}
inline void precalc(std::vector < int > &r, int tmax, int l, std::vector < std::vector < int > > &comb) {
std::vector < int > combL(std::min(tmax + 1, l + 1));
calcCombinari(combL, l);
for (int i = 0; i <= tmax; i++) {
r[i] = 0;
for (int j = 1; j <= i && j <= l; j++)
r[i] = (r[i] + 1LL * comb[i - 1][j - 1] * combL[j]) % MOD;
}
}
inline void solve(std::vector < std::vector < int > > &dp, int n, int l, int &w, int &q, std::vector < bool > &avem, std::vector < std::vector < int > > &comb) {
w = 1 - w;
q = 1 - q;
int tmax = 0;
for (int i = 1; i <= n; i++)
tmax += avem[i];
std::vector < int > r(tmax + 1);
precalc(r, tmax, l, comb);
for (int i = 0; i <= n; i++)
dp[w][i] = 0;
for (int i = 0; i <= n; i++) {
dp[w][i] = (dp[w][i] + dp[q][i]) % MOD;
int t = 0;
for (int j = i + 1; j <= n; j++) {
if (avem[j]) {
t++;
dp[w][j] = (dp[w][j] + 1LL * dp[q][i] * r[t]) % MOD;
}
}
}
}
int main() {
int n;
fscanf(fin, "%d", &n);
std::vector < std::vector < int > > comb(n, std::vector < int > (n, 0));
precalcCombinari(comb);
std::vector < int > poz, A(n + 1), B(n + 1);
for (int i = 1; i <= n; i++) {
fscanf(fin, "%d%d", &A[i], &B[i]);
poz.push_back(A[i]);
poz.push_back(B[i] + 1);
}
std::sort(poz.begin(), poz.end());
poz.resize(std::distance(poz.begin(), std::unique(poz.begin(), poz.end())));
int w = 0, q = 1;
std::vector < std::vector < int > > dp(2, std::vector < int > (n + 1, 0));
dp[0][0] = 1;
std::vector < bool > avem(n + 1);
for (int i = 0; i < (int)poz.size() - 1; i++)
if (getValues(n, poz[i], poz[i + 1], A, B, avem))
solve(dp, n, poz[i + 1] - poz[i], w, q, avem, comb);
int ans = 0;
for (int i = 1; i <= n; i++)
ans = (ans + dp[w][i]) % MOD;
fprintf(fout, "%d\n", ans);
fclose(fin);
fclose(fout);
return 0;
}
