Submission #1205708

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Source Code Expand

#include <cmath>
#include <cstdlib>
#include <iostream>
int factorial(const int &value) {
    int ret = 1;
    for (int i = 0; i < value; ++i) {
        ret *= i + 1;
    }
    return ret;
}
int main(void) {
    const int mod = pow(10.0, 9.0) + 7;
    int n;
	while (std::cin >> n) {
		int ans = 1, stack = 0, *arr;
		arr = new int[n];
		for (int i = 0; i < n; ++i) {
			std::cin >> arr[i];
		}
		for (int i = 0; i < n; ++i) {
			int x = arr[i];
			if (x < 2 * ++stack - 1) {
				ans *= stack--;
				ans %= mod;
       	 }
    	}
		ans *= factorial(stack) % mod;
		ans %= mod;
		std::cout << ans << std::endl;
		delete[] arr;
	}
	return EXIT_SUCCESS;
}

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