/* -*- coding: utf-8 -*- * * 1127.cc: No.1127 変形パスカルの三角形 - yukicoder */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; /* constant */ const int MAX_N = 200000; const int MOD = 1000000007; /* typedef */ typedef long long ll; /* global variables */ int fs[MAX_N + 1], invfs[MAX_N + 1]; /* subroutines */ int powmod(int a, int n) { // a^n % MOD int pm = 1; while (n > 0) { if (n & 1) pm = (ll)pm * a % MOD; a = (ll)a * a % MOD; n >>= 1; } return pm; } inline int nck(int n, int k) { // nCk % MOD return (ll)fs[n] * invfs[n - k] % MOD * invfs[k] % MOD; } void prepare_fracs(int n) { fs[0] = invfs[0] = 1; for (int i = 1; i <= n; i++) { fs[i] = (ll)fs[i - 1] * i % MOD; invfs[i] = powmod(fs[i], MOD - 2); } } inline int calcnk(int n, int k, ll a, ll b) { return (nck(n - 1, k) * a % MOD + nck(n - 1, k - 1) * b % MOD) % MOD; } /* main */ int main() { ll a, b; int n, k; scanf("%lld%lld%d%d", &a, &b, &n, &k); a %= MOD, b %= MOD; k--; prepare_fracs(n); int c = (k == 0) ? a : (k == n) ? b : calcnk(n, k, a, b); int sum = ((ll)a * a % MOD + (ll)b * b % MOD) % MOD; for (int i = 1; i < n; i++) { int d = calcnk(n, i, a, b); sum = (sum + (ll)d * d % MOD) % MOD; } printf("%d\n%d\n", c, sum); return 0; }