public class Main {
private static void solve() {
int n = ni();
int max = 2000;
int m = max * 2 + 1;
int[][] cnt = new int[m][m];
int mod = 1000000000 + 7;
int[][] fif = enumFIF(4010, mod);
long z = 0;
for (int i = 0; i < n; i ++) {
int a = ni();
int b = ni();
cnt[max - a][max - b] --;
cnt[max + a][max + b] ++;
z += CX((a + b) * 2, a * 2, mod, fif);
z %= mod;
}
long[][] dp = new long[m][m];
long ret = 0;
for (int i = 0; i < m; i ++) {
for (int j = 0; j < m; j ++) {
if (cnt[i][j] < 0) {
dp[i][j] += -cnt[i][j];
} else if (cnt[i][j] > 0) {
ret += dp[i][j] * cnt[i][j];
ret %= mod;
}
if (i < m - 1) {
dp[i + 1][j] += dp[i][j];
dp[i + 1][j] %= mod;
}
if (j < m - 1) {
dp[i][j + 1] += dp[i][j];
dp[i][j + 1] %= mod;
}
}
}
System.out.println((ret + mod - z) * invl(2, mod) % mod);
}
public static long invl(long a, long mod)
{
long b = mod;
long p = 1, q = 0;
while(b > 0){
long c = a / b;
long d;
d = a; a = b; b = d % b;
d = p; p = q; q = d - c * q;
}
return p < 0 ? p + mod : p;
}
public static long CX(long n, long r, int p, int[][] fif)
{
if(n < 0 || r < 0 || r > n)return 0;
int np = (int)(n%p), rp = (int)(r%p);
if(np < rp)return 0;
if(n == 0 && r == 0)return 1;
int nrp = np-rp;
if(nrp < 0)nrp += p;
return (long)fif[0][np]*fif[1][rp]%p*fif[1][nrp]%p*CX(n/p, r/p, p, fif)%p;
}
public static int[][] enumFIF(int n, int mod)
{
int[] f = new int[n+1];
int[] invf = new int[n+1];
f[0] = 1;
for(int i = 1;i <= n;i++){
f[i] = (int)((long)f[i-1] * i % mod);
}
long a = f[n];
long b = mod;
long p = 1, q = 0;
while(b > 0){
long c = a / b;
long d;
d = a; a = b; b = d % b;
d = p; p = q; q = d - c * q;
}
invf[n] = (int)(p < 0 ? p + mod : p);
for(int i = n-1;i >= 0;i--){
invf[i] = (int)((long)invf[i+1] * (i+1) % mod);
}
return new int[][]{f, invf};
}
public static void main(String[] args) {
new Thread(null, new Runnable() {
@Override
public void run() {
long start = System.currentTimeMillis();
String debug = args.length > 0 ? args[0] : null;
if (debug != null) {
try {
is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
solve();
out.flush();
tr((System.currentTimeMillis() - start) + "ms");
}
}, "", 64000000).start();
}
private static java.io.InputStream is = System.in;
private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
private static java.util.StringTokenizer tokenizer = null;
private static java.io.BufferedReader reader;
public static String next() {
while (tokenizer == null || !tokenizer.hasMoreTokens()) {
try {
tokenizer = new java.util.StringTokenizer(reader.readLine());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return tokenizer.nextToken();
}
private static double nd() {
return Double.parseDouble(next());
}
private static long nl() {
return Long.parseLong(next());
}
private static int[] na(int n) {
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = ni();
return a;
}
private static char[] ns() {
return next().toCharArray();
}
private static long[] nal(int n) {
long[] a = new long[n];
for (int i = 0; i < n; i++)
a[i] = nl();
return a;
}
private static int[][] ntable(int n, int m) {
int[][] table = new int[n][m];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[i][j] = ni();
}
}
return table;
}
private static int[][] nlist(int n, int m) {
int[][] table = new int[m][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[j][i] = ni();
}
}
return table;
}
private static int ni() {
return Integer.parseInt(next());
}
private static void tr(Object... o) {
if (is != System.in)
System.out.println(java.util.Arrays.deepToString(o));
}
}