const MOD: usize = 1e9 as usize + 7; fn fact_inv(size: usize) -> (Vec, Vec) { let mut facts = vec![0usize; size+1]; let mut fact_invs = vec![0usize; size+1]; let mut invs = vec![0usize; size+1]; facts[0] = 1; facts[1] = 1; fact_invs[0] = 1; fact_invs[1] = 1; invs[1] = 1; for i in 2..=size { facts[i] = facts[i-1] * i % MOD; invs[i] = MOD - invs[MOD % i] * (MOD / i) % MOD; fact_invs[i] = fact_invs[i - 1] * invs[i] % MOD; } (facts, fact_invs) } fn comb(n: usize, r: usize, facts: &Vec, fact_invs: &Vec) -> usize { facts[n] * fact_invs[r] % MOD * fact_invs[n-r] % MOD } fn main() { let mut nmk = String::new(); std::io::stdin().read_line(&mut nmk).ok(); let nmk: Vec = nmk.trim().split_whitespace().map(|s| s.parse().unwrap()).collect(); let n = nmk[0]; let m = nmk[1]; let k = nmk[2]; let mut perms = vec![1usize; n.max(m)+1]; for i in 0..n.max(m) { perms[i+1] = perms[i] * (i+1) % MOD; } let (facts, fact_invs) = fact_inv(n+m+10); let mut result = 0usize; for i in 1..=n.min(m) { let total = n+m - 2*i; if total < k { continue; } result += perms[n-1] * perms[m] % MOD * comb(n, i, &facts, &fact_invs) % MOD * comb(m-1, i-1, &facts, &fact_invs) % MOD; result %= MOD; } println!("{}", result); }