#include <stdio.h>
#include <math.h>


double F(double x)
{
    return x - sin(x);
}
double integral(double a, double b)
{
    return (pow(b,2)/2 + cos(b)) - (pow(a,2)/2 + cos(a));
}


double solve(double a, double b, int n)
{
    int i;
    double dx, sum = 0, lastF, nextF;
    dx = (b-a)/n;
    lastF = F(a);
    for(i = 1; i <= n; i++)
    {
        nextF = F(a + i*dx);
        sum += ((lastF + nextF)/2)*dx;
        lastF = nextF;

    }
    return sum;
}

int main() {
    int n;
    double a, b, result;

    printf("Enter number of segments: ");
    scanf("%d", &n);
    printf("\n");
    printf("Enter range (0 9.81): ");
    scanf("%lf %lf", &a, &b);
    printf("\n");

    printf("n = %d a = %lf b = %lf\n\n", n, a, b);

    result = solve(a, b, n);
    printf("result            %lf\n", result);
    printf("real integral %lf\n", integral(a, b));

    return 0;
}