浮点数二分

#include <iostream>

using namespace std;

int main(){
    double x;
    cin >> x;
    
    double l = 0, r = x;
    
    while(r - l > 1e-8){
        //这里有精度问题所以整大点 1e-8
        double mid = (l + r) / 2;
        if(mid * mid >= x) r = mid;
        else l = mid;
    }
    
    printf("%lf\n", l);
    
    return 0;
}