Binomial distribution

BinomialDistributionCalculator.cpp

/*
Input: x,n,p (Each inputs should separated by space or line) 
Output: b(x,n,p)
*/
#include<iostream>
#include<cmath>
using namespace std;
long long int factorial(int n){
    long long int _result=1;
    for(int _n = n;n>=1;n--){
        _result = _result*n;
    }
    return _result;
}

long long int combination(int n,int x){
    return factorial(n)/(factorial(x)*factorial(n-x));
}

int main(){
    int x,n;
    double p;
    while(cin>>x>>n>>p){
         cout<<combination(n,x)*pow(p,x)*pow(1-p,n-x)<<endl;
    }
}