Submission #1232765

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Source Code Expand

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <set>
using namespace std;

long long M=1000000007;
int main(int argc, char const *argv[]) {
  long long n,d;cin>>n>>d;
  int pri[3]={2,3,5},num[3]={0,0,0};
  for(int i=0;i<3;++i){
    while(d%pri[i]==0){
      num[i]++;
      d/=pri[i];
    }
  }
  if(d!=1){
    cout<<0.0<<endl;
    return 0;
  }
  vector<vector<vector<double>>> dp(2*n+3,vector<vector<double>>(n+1,vector<double>(n+1,0.0)));
  dp[0][0][0]=1.0;
  for(int t=0;t<n;++t){
    vector<vector<vector<double>>> dp1(2*n+3,vector<vector<double>>(n+1,vector<double>(n+1,0.0)));
    for(int i=0;i<=2*t;++i)for(int j=0;j<=t;++j)for(int k=0;k<=t;++k){
      dp1[i][j][k]+=dp[i][j][k]/6.0;
      dp1[i+1][j][k]+=dp[i][j][k]/6.0;
      dp1[i][j+1][k]+=dp[i][j][k]/6.0;
      dp1[i+2][j][k]+=dp[i][j][k]/6.0;
      dp1[i+1][j+1][k]+=dp[i][j][k]/6.0;
      dp1[i][j][k+1]+=dp[i][j][k]/6.0;
    }
    dp=dp1;
  }
  double res=0.0;
  for(int i=0;i<=2*n;++i)for(int j=0;j<=n;++j)for(int k=0;k<=n;++k){
    if(i>=num[0]&&j>=num[1]&&k>=num[2])res+=dp[i][j][k];
  }
  cout<<setprecision(10)<<res<<endl;
  return 0;
}

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