// Copyright (C) 2017 __debug.

// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; version 3

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; If not, see <http://www.gnu.org/licenses/>.


#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/priority_queue.hpp>

#define x first
#define y second
#define MP std::make_pair
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(), (x).end()
#define DEBUG(...) fprintf(stderr, __VA_ARGS__)
#ifdef __linux__
#define getchar getchar_unlocked
#define putchar putchar_unlocked
#endif

using std::pair;
using std::vector;
using std::string;

typedef long long LL;
typedef pair<int, int> Pii;

const int oo = 0x3f3f3f3f;

template<typename T> inline bool chkmax(T &a, T b) { return a < b ? a = b, true : false; }
template<typename T> inline bool chkmin(T &a, T b) { return b < a ? a = b, true : false; }
string procStatus()
{
    std::ifstream t("/proc/self/status");
    return string(std::istreambuf_iterator<char>(t), std::istreambuf_iterator<char>());
}
template<typename T> T read(T &x)
{
    int f = 1;
    char ch = getchar();
    for (; !isdigit(ch); ch = getchar())
        f = (ch == '-' ? -1 : 1);
    for (x = 0; isdigit(ch); ch = getchar())
        x = 10 * x + ch - '0';
    return x *= f;
}
template<typename T> void write(T x)
{
    if (x == 0) {
        putchar('0');
        return;
    }
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    static char s[20];
    int top = 0;
    for (; x; x /= 10)
        s[++top] = x % 10 + '0';
    while (top)
        putchar(s[top--]);
}
// EOT

const int MAXN = 2e5 + 5, RNG = 2e3 + 5;
const int MOD = 1e9 + 7;

int N;
Pii A[MAXN];

void input()
{
    read(N);
    for (int i = 1; i <= N; ++i) {
        read(A[i].x); read(A[i].y);
    }
}

int fac[RNG * 4], ifac[RNG * 4];

LL fpm(LL base, LL exp)
{
    LL ret = 1;
    for (; exp; exp >>= 1) {
        if (exp & 1)
            (ret *= base) %= MOD;
        (base *= base) %= MOD;
    }
    return ret;
}

inline int C(int n, int k)
{
    assert(0 <= k && k <= n);
    return (LL)fac[n] * ifac[k] % MOD * ifac[n - k] % MOD;
}

void solve()
{
    fac[0] = 1;
    for (int i = 1; i < RNG * 4; ++i) {
        fac[i] = (LL)fac[i - 1] * i % MOD;
    }
    ifac[RNG * 4 - 1] = fpm(fac[RNG * 4 - 1], MOD - 2);
    for (int i = RNG * 4 - 1; i >= 1; --i) {
        ifac[i - 1] = (LL)ifac[i] * i % MOD;
    }

    static int dp[RNG * 2][RNG * 2];
    static int cnt[RNG * 2][RNG * 2];
    int ans = 0;

    for (int i = 1; i <= N; ++i) {
        dp[RNG - A[i].x][RNG - A[i].y] += 1;
        cnt[RNG + A[i].x][RNG + A[i].y] += 1;
        (ans += MOD - C(A[i].x * 2 + A[i].y * 2, A[i].x * 2)) %= MOD;
    }
    for (int i = 0; i < RNG * 2; ++i) {
        for (int j = 0; j < RNG * 2; ++j) {
            (dp[i][j] += (i ? dp[i - 1][j] : 0) + (j ? dp[i][j - 1] : 0)) %= MOD;
            (ans += (LL)cnt[i][j] * dp[i][j] % MOD) %= MOD;
        }
    }
    ans = (LL)ans * fpm(2, MOD - 2) % MOD;

    printf("%d\n", ans);
}

int main()
{
#ifdef __DEBUG
    freopen("E.in", "r", stdin);
    freopen("E.out", "w", stdout);
#endif

    input();
    solve();

    return 0;
}

// 念兰堂红烛，心长焰短，向人垂泪。
//     -- 晏殊《撼庭秋·别来音信千里》


Measured memory_bytes: 96384