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| #include <stdio.h> |
| #include <ctype.h> |
| #include <stdlib.h> |
| |
| #define gc() getchar() |
| #define MAXN 1000000 |
| using namespace std; |
| |
| const long long MOD = 1000000007; |
| |
| long long fact[1000007]; |
| long long N, A, B, D; |
| |
| inline long long modpow(long long base, long long exp, long long modulus) |
| { |
| long long result = 1; |
| |
| base %= modulus; |
| |
| while (exp > 0) |
| { |
| if (exp & 1) |
| result = (result * base) % modulus; |
| |
| base = (base * base) % modulus; |
| exp >>= 1; |
| } |
| |
| return result; |
| } |
| |
| inline bool finish() |
| { |
| char c = gc(); |
| |
| while (isspace(c)) |
| c = gc(); |
| |
| if (c == EOF) |
| { |
| ungetc(c, stdin); |
| return 1; |
| } |
| |
| ungetc(c, stdin); |
| return 0; |
| } |
| |
| inline void pre() |
| { |
| int i; |
| |
| fact[0] = 1; |
| |
| for (i = 1; i <= MAXN; i++) |
| { |
| fact[i] = fact[i - 1] * i; |
| fact[i] %= MOD; |
| } |
| } |
| |
| inline long long rev(long long num) |
| { |
| return modpow(num, MOD - 2, MOD); |
| } |
| |
| inline long long ncr(long long n, long long k) |
| { |
| long long res = fact[n]; |
| |
| res *= rev(fact[k]); |
| res %= MOD; |
| |
| res *= rev(fact[n - k]); |
| res %= MOD; |
| |
| return res; |
| } |
| |
| inline void init() |
| { |
| scanf("%lld %lld %lld %lld", &N, &A, &B, &D); |
| } |
| |
| inline long long solve() |
| { |
| long long res = ncr(N, A); |
| |
| res *= modpow(ncr(B, D), A, MOD); |
| res %= MOD; |
| |
| return res; |
| } |
| |
| int main() |
| { |
| |
| |
| pre(); |
| |
| while (!finish()) |
| { |
| init(); |
| printf("%lld\n", solve()); |
| } |
| |
| return 0; |
| } |
|
|
