#include<bits/stdc++.h>
using namespace std;
#define rep(i, N) for(i = 0; i < N; i++)
#define ll long long

int main(void) {
    ll N;
    ll L[8];
    ll R[8];
    
    ll i, j, k;

    cin>>N;
    rep(i, 8) cin>>L[i]>>R[i];

    vector<ll>P;
    rep(i,N)P.push_back(i);

    ll ans=0;
    do{
        bool can=1;
        ll now=0;
        rep(i,N){
            now=max(now,L[P[i]]);
            if(R[P[i]]<now)can=0;
        }
        ans+=can;
    }while(next_permutation(P.begin(), P.end()));

    cout<<ans<<endl;

    return 0;
}