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

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

double trap(double a,double b){
    return (f(a)+f(b))/2*(b-a);
}
double g(double u,double a,double b){
    return f((b-a)/2*u+(b+a)/2)*(b-a)/2;
}
double gauss3(double a,double b){
    return g(0,a,b)/0.3e1 
        +0.5e1/0.6e1*g(sqrt(0.10e2)/0.5e1,a,b)
        +0.5e1/0.6e1*g(-sqrt(0.10e2)/0.5e1,a,b);
}

double quad(double a,double b){
    double y1=trap(a,b);
    double y2=gauss3(a,b);
    if(fabs(y1-y2)<1e-7*(b-a)) return y2;
    double m=(a+b)/2;
    double r1=quad(a,m);
    double r2=quad(m,b);
    return r1+r2;
}

int main(){
    printf("I=%24.15e\n",quad(-1.0,1.0));
    return 0;
}