#include <stdio.h>
  #include <stdlib.h>
  
  double f(double x){
    return sin(x);
  }


int main(int argc, char** argv) {
  
  double a, b, delx, x, y, tot;
  int n, i;
  
  a = 0.0;
  b=3.141592653589793;
  n = atoi(argv[1]);

  delx = (b-a)/n;
  x = a;
  tot = 0.0;

  for(i=1;i<n;++i){
    x = a + i*delx;
    y=f(x);
    tot = tot + y;
  }

  tot = delx * ((f(a)+f(b))/2.0 + tot);

  printf("approximate integral using %d intervals = %lf\n", n,tot);

  return 0;
}