#include <stdio.h>

double traps(double a, double b, int n,double (*f)(double));
double f(double x);
int main(void) {
  double s;
  s = traps(0,1,1000,f);
  printf("%f \n",s);
}

double traps(double a, double b, int n,double (*f)(double)) {
  double s;
  double h;
  double a_;
  int i;
  
  h = (b-a)/n; 
  a_ =a+h;
  
  s =(f(a) + f(b))*0.5;
  for(i =1; i<n;i++) {
    s += (*f)(a_);
    a_+=h;
      
  }
  return s*h;
}

double f(double x)
{
  return x*x*x;
}