/*
#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")
#pragma GCC optimize("unroll-loops")
*/
#include <bits/stdc++.h>
#define int long long
#define float double
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define endl '\n'
#define pii pair<int, int>
using namespace std;
const int mxN = 3005;
const int mod = 1e9 + 7;
int r, c, n, f[mxN][mxN], fact[mxN], revfact[mxN];
int binpow(int x, int y){
int res = 1;
while(y != 0){
if(y % 2 == 1) res = (res * x) % mod;
x = (x * x) % mod;
y /= 2;
}
return res;
}
void calcfact(){
fact[0] = revfact[0] = 1;
for(int i = 1; i < mxN; ++i){
fact[i] = (fact[i - 1] * i) % mod;
revfact[i] = binpow(fact[i], mod - 2);
}
}
int kCr(int k, int r){
int res = 1;
res = (res * fact[r]) % mod;
res = (res * revfact[k]) % mod;
res = (res * revfact[r - k]) % mod;
return res;
}
int factorial(int x){
int res = 1;
for(int i = 1; i <= x; ++i){
res = (res * i) % mod;
}
return res;
}
void solve(){
cin >> r >> c >> n;
int minx, maxx, miny, maxy;
maxy = maxx = INT_MIN;
miny = minx = INT_MAX;
for(int i = 1; i <= n; ++i){
cin >> a[i].x >> a[i].y;
maxx = max(maxx, a[i].x);
minx = min(minx, a[i].x);
miny = min(miny, a[i].y);
maxy = max(maxy, a[i].y);
}
int disx = maxx - minx + 1, disy = maxy - miny + 1;
int ans = disx * disy - n;
ans = factorial(ans);
//cout << disx << " " << disy << endl;
f[r][c] = 1;
calcfact();
for(int i = r - 1; i >= disx; --i){
f[i][c] = (f[i + 1][c] * fact[c]) % mod;
}
for(int i = c - 1; i >= disy; --i){
f[r][i] = (f[r][i + 1] * fact[r]) % mod;
}
for(int i = r - 1; i >= disx; --i){
for(int j = c - 1; j >= disy; --j){
f[i][j] += (f[i + 1][j] * fact[j]) % mod;
f[i][j] += (f[i][j + 1] * fact[i]) % mod;
f[i][j] %= mod;
//cout << i << " " << j << " " << f[i][j] << endl;
}
}
ans = (ans * f[disx][disy]) % mod;
ans = (ans * kCr(minx - 1, r - disx)) % mod;
ans = (ans * kCr(miny - 1, c - disy)) % mod;
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
//freopen("Bai3.inp", "r", stdin);
//freopen("Bai3.out", "w", stdout);
solve();
}
Compilation message
mascots.cpp: In function 'void solve()':
mascots.cpp:55:16: error: 'a' was not declared in this scope
55 | cin >> a[i].x >> a[i].y;
| ^
