#include <stdio.h>
#include <stdlib.h>

int main() {
    int n,i;
    double x;
    double f = 1;
    printf("Input n: ");
    scanf("%d",&n);
    do{
        printf("Input x: ");
        scanf("%lf", &x);
        if(((x-(int)x) < 0.0000001)&&((int)x<=2*n))
            printf("Division by zero. Input other X. \n");
    }while(((x-(int)x) < 0.0000001)&&((int)x<=2*n));
    for( i=1 ; i<=n ; i++){
        f*=(x-(2*i-1))/(x-2*i);
    }
    printf("f=%lf \n",f);
    system("PAUSE");
    return 0;
}