#include<bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define MP make_pair
#define PB push_back
#define ll long long
#define pii pair<int, int>
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define MS(a, v) memset(a, v, sizeof a)
#define REP(i, n) for(int i = 0; i < n; ++ i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++ i)
#define FOD(i, a, b) for(int i = (a); i >= (b); -- i)
#define TSun(TZ) freopen(TZ".inp", "r", stdin), freopen(TZ".ans", "w", stdout)

template<class X, class Y>
        bool maximize(X & x, const Y & y){
                if(x < y){
                        x = y;
                        return true;
                }
                else return false;
        }

template<class X, class Y>
        bool minimize(X & x, const Y & y){
                if(x > y){
                        x = y;
                        return true;
                }
                else return false;
        }

const int MAXN = 200005;
const int MOD = 1e9 + 7;
const ll INF = 1e18;

int sum(int a, int b){
        return a + b >= MOD ? a + b - MOD : a + b;
}

void add(ll &a, int b){
        a += b;
        if(a >= MOD) a -= MOD;
}

int Pow(int a, int b){
        int res = 1;
        while(b > 0){
                if(b & 1){
                        res = 1ll * res * a % MOD;
                }
                b >>= 1; a = 1ll * a * a % MOD;
        }
        return res;
}

int n, a[MAXN], b[MAXN], C[4004][4004];

namespace sub1{
        bool check(void){
                return n <= 2000;
        }

        void solve(void){
                ll res = 0;
                FOR(i, 1, n){
                        FOR(j, i + 1, n){
                                int x = a[i] + a[j];
                                int y = b[i] + b[j];
                                add(res, C[x + y][x]);
                        }
                }
                cout << res;
        }
}

namespace sub2{
        bool check(void){
                return *max_element(a + 1, a + n + 1) <= 100 && *max_element(b + 1, b + n + 1) <= 100;
        }

        int dd[101][101];

        void solve(void){
                ll res = 0;
                FOR(i, 1, n)
                        ++ dd[ a[i] ][ b[i] ];

                int u2 = Pow(2, MOD - 2);

                FOR(i, 1, 100) FOR(j, 1, 100) if(dd[i][j]){
                        FOR(u, 1, 100) FOR(v, 1, 100) if(dd[u][v]){
                                ll c1 = dd[i][j], c2 = dd[u][v];
                                int x = i + u, y = j + v;
                                ll val = C[x + y][y];
                                if(u == i && v == j)
                                        add(res, val * ((c1 * (c1 - 1) / 2) % MOD) % MOD);
                                else
                                        add(res, val * c1 % MOD * c2 % MOD);
                        }
                }
                cout << res * u2 % MOD;
        }
}


void solve(void){
        cin >> n;
        FOR(i, 1, n) cin >> a[i] >> b[i];

        FOR(i, 0, 2000) C[i][0] = 1;
        FOR(i, 1, 2000)
                FOR(j, 1, i)
                        C[i][j] = sum(C[i - 1][j], C[i - 1][j - 1]);

//        if(sub1 :: check())
//                return sub1 :: solve();
        if(sub2 :: check())
                return sub2 :: solve();
}

int main(void){

        ios_base :: sync_with_stdio(0);
        cin.tie(0); cout.tie(0);

        #define TaZinh "test"

        if(fopen(TaZinh".inp", "r"))
                TSun(TaZinh);

        int Sun = 1;
//        cin >> Sun;
        REP(love, Sun) solve();

        return 0;
}