Submission #2114242

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

int main() {
	int64_t n, d;
	cin >> n >> d;
	double dp[n + 1][71][71][71]{};
	dp[0][0][0][0] = 1;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < 71; j++) {
			for (int k = 0; k < 71; k++) {
				for (int l = 0; l < 71; l++) {
					dp[i + 1][j][k][l] += dp[i][j][k][l] / 6;
					dp[i + 1][min(70, j + 1)][k][l] += dp[i][j][k][l] / 6;
					dp[i + 1][j][min(70, k + 1)][l] += dp[i][j][k][l] / 6;
					dp[i + 1][min(70, j + 2)][k][l] += dp[i][j][k][l] / 6;
					dp[i + 1][j][k][min(70, l + 1)] += dp[i][j][k][l] / 6;
					dp[i + 1][min(70, j + 1)][min(70, k + 1)][l] += dp[i][j][k][l] / 6;
				}
			}
		}
	}
	int a = 0, b = 0, c = 0;
	while (d % 2 == 0) {
		a++;
		d /= 2;
	}
	while (d % 3 == 0) {
		b++;
		d /= 3;
	}
	while (d % 5 == 0) {
		c++;
		d /= 5;
	}
	if (d != 1) {
		cout << 0 << endl;
		return 0;
	}
	double ans = 0;
	for (int j = a; j < 71; j++) {
		for (int k = b; k < 71; k++) {
			for (int l = c; l < 71; l++) {
				ans += dp[n][j][k][l];
			}
		}
	}
	cout << fixed << setprecision(10) << ans << endl;
	return 0;
}

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