Asif 2(c)

#include<stdio.h>
#include<math.h>

int fact(int n)
{
    int value = 1;
    for(int i=1;i<=n;i++)
        value *= i;
    return value;
}
int main()
{
    int n;
    scanf("%d",&n);
    double ans = 1.0;
    double temp = 1;
    for(int i=1;i<n;i++){
        temp += 2;
        double value = (double)fact(temp);
        value = 1.0/value;
        if(i%2==1){
            ans -= value;
        }
        else{
            ans += value;
        }
    }
    printf("%.4lf\n",ans);
    return 0;
}