#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 quad(double a,double b){
    if(fabs(b-a)<1e-4) return trap(a,b);
    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;
}