#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr ll INFLL = numeric_limits<ll>::max() / 2;
template<class T>
istream &operator>>(istream &is, vector<T> &a) {
for (auto &i : a) {
is >> i;
}
return is;
}
vector<pair<int, int>> lr;
vector<int> used;
struct SegTree {
struct Node {
int mx = -INF, imx = -1, mn = INF, imn = -1;
Node() = default;
Node(int v, int i) {
mx = mn = v;
imx = imn = i;
}
};
Node pull(const Node &a, const Node &b) {
Node ans;
if (a.mx > b.mx) {
ans.mx = a.mx;
ans.imx = a.imx;
} else {
ans.mx = b.mx;
ans.imx = b.imx;
}
if (a.mn < b.mn) {
ans.mn = a.mn;
ans.imn = a.imn;
} else {
ans.mn = b.mn;
ans.imn = b.imn;
}
return ans;
}
vector<Node> tree;
int n;
SegTree() {}
SegTree(int n) : n(n) {
tree.resize(4 * n);
}
void update(int v, int l, int r, int i, int x) {
if (l + 1 == r) {
tree[v] = {x, l};
return;
}
int m = (l + r) / 2;
if (i < m) {
update(2 * v + 1, l, m, i, x);
} else {
update(2 * v + 2, m, r, i, x);
}
tree[v] = pull(tree[2 * v + 1], tree[2 * v + 2]);
}
void update(int i, int x) {
update(0, 0, n, i, x);
}
Node get(int v, int l, int r, int li, int ri) {
if (li >= r || l >= ri) {
return Node();
}
if (li <= l && r <= ri) {
return tree[v];
}
int m = (l + r) / 2;
return pull(get(2 * v + 1, l, m, li, ri), get(2 * v + 2, m, r, li, ri));
}
Node get(int li, int ri) {
return get(0, 0, n, li, ri);
}
};
SegTree st1, st2;
vector<pair<int, int>> v;
void dfs(int i, int c) {
used[i] = c;
auto [li, ri] = lr[i];
st1.update(li, -INF);
st2.update(ri, INF);
while (1) {
auto [mx, j, kek1, kek2] = st1.get(li, ri);
if (mx < ri) {
break;
}
assert(used[v[j].first] == -1);
dfs(v[j].first, c ^ 1);
}
while (1) {
auto [kek1, kek2, mn, j] = st2.get(li, ri);
if (mn > li) {
break;
}
assert(used[v[j].first] == -1);
dfs(v[j].first, c ^ 1);
}
// for (int j = 0; j < (int) lr.size(); ++j) {
// if (i == j || used[j] != -1) {
// continue;
// }
// auto [li, ri] = lr[i];
// auto [lj, rj] = lr[j];
// if (li < lj && lj < ri && rj > ri) { // li lj ri rj
// dfs(j, c ^ 1);
// }
// if (li < rj && rj < ri && lj < li) { // lj li rj ri
// dfs(j, c ^ 1);
// }
// }
}
int main() {
cin.tie(0)->sync_with_stdio(0);
#ifdef __APPLE__
freopen("input.txt", "r", stdin);
#endif
int n;
cin >> n;
lr.resize(n);
v.resize(2 * n);
for (int i = 0; i < n; ++i) {
int a, b;
cin >> a >> b;
--a;
--b;
lr[i] = {a, b};
v[a] = {i, 1};
v[b] = {i, -1};
}
used.resize(n, -1);
st1 = SegTree(2 * n);
st2 = SegTree(2 * n);
for (int i = 0; i < n; ++i) {
auto [l, r] = lr[i];
st1.update(l, r);
st2.update(r, l);
}
int cnt = 0;
for (int i = 0; i < n; ++i) {
if (used[i] == -1) {
dfs(i, 0);
++cnt;
}
}
vector<vector<int>> chel(2);
bool ok = 1;
for (int i = 0; i < 2 * n; ++i) {
if (v[i].second == 1) {
chel[used[v[i].first]].push_back(lr[v[i].first].second);
} else {
if (!chel[0].empty() && chel[0].back() == i) {
chel[0].pop_back();
} else if (!chel[1].empty() && chel[1].back() == i) {
chel[1].pop_back();
} else {
ok = 0;
break;
}
}
}
if (!ok) {
cout << 0;
} else {
ll ans = 1;
constexpr int mod = 1e9 + 7;
for (int i = 0; i < cnt; ++i) {
(ans *= 2) %= mod;
}
cout << ans;
}
}
