fn s(a:f64,b:i32) -> f64 {
    let mut th1 = 1.0;
    let mut th2 = 0.0;
    let mut th3 = 0.0;
    let mut k = 0;
    while k < b{
        while th3 * th3 < a{
            th2 = th3;
            th3 = th3 + th1;
        }
        th3 = th2;
        th1 = th1 * 0.1;
        k += 1;
    }
    th3
}

fn main() {
    println!("結果:{}",s(2.0,10));
}