#include<stdio.h>

double integral(double a, double b, int n, double (*fp)(double)){
	double h, sum;

	h = (b-a) / n;
	sum = ((*fp)(a) + 4*(*fp)(a+h)+2*(*fp)(a+2*h));

	int j;

	for(j = 1; j < n; j++){
		sum += (2*(*fp)(a+(j-1)*h))+(4*(*fp)(a+j*h))+(*fp)(b) ;
	}

	return h/3 * sum;
}

double quadratic(double x)
{
	return x*x + 5.0*x + 3.0;
}

int main()
{

	while(1)
	{
		double x;
		double a,b;
		printf("Input batas bawah integral = ");
		scanf("%lf",&a);
		printf("\n");

		printf("Input batas atas integral = ");
		scanf("%lf",&b);
		printf("\n");

		printf("Input variabel n = ");
		scanf("%lf",&x);
		printf("\n");


//		if(x%2==0){
		printf("%.2lf\n",integral(a, b, x, quadratic));
//		}

//		else{
//			printf("Variabel n harus berbentuk angka genap\n");
//		}
	}

	return 0;
}