#include <math.h>
#include <stdio.h>
double func(double x)
{
 return x*(x+3);
}

double simp() {
    double a, b;
        int m = 10;
    printf("Input a\n");
    scanf("%lf", &a);
    printf("Input b\n");
    scanf("%lf", &b);
    double h = (b - a) / m;
    double sum = 0;

    double x0 = a;
    double x1 = a + h;

    for (int i=0; i<=m-1; i++) {
        sum += (h/3)*(2*func(x0 + h/2) + (func(x0)+ func(x1))/2);

        x0 += h;
        x1 += h;
    }

    return sum;
}

double rect()
{
    double a, b;
    printf("Input a\n");
    scanf("%lf", &a);
    printf("Input b\n");
    scanf("%lf", &b);
    int m=10, eps=0.0001;
    double sum = 0.0, t=0.0, tp=eps+1;
    double h = ((b-a)/m);
    for (double x = a; x <=b; x+=h, fabs(t-tp)>eps){
        sum += t;
        tp = t;
        t= h*(func(x-h/2));
    }

    return sum;
}


int main()
{
  int w = 1;
  while(w==1){
  int inp;
  double ans=0;
  printf("Please choose what to execute: 1- Simpson's method, 2 - Rectangles\n");
  scanf("%d", &inp);
  switch (inp)
  {
     case 1:
     {
         ans = simp();
         printf("%f\n",ans);

     break;
         }
     case 2:
     {
                 ans = rect();
                 printf("%f\n", ans);
     break;
     }
         default:
     {
     printf("Input right value!\n");
         break;
         }


     }
     printf("Continue?\n");
     scanf("%d",&w);
  }
  return 0;
}