#include using namespace std; int main(){ int n; cin>>n; vector l(n),r(n); for (int i=0;i>l[i]>>r[i]; vector p(n); iota(p.begin(),p.end(),0); int ans=0; do{ int m=0; bool ok=true; for (int i=0;ir[p[i]]){ ok=false; } m=max(m,l[p[i]]); } ans+=ok; }while(next_permutation(p.begin(),p.end())); cout<