窝久布用韩束

代码如下

#include<bits/stdc++.h>
using namespace std;
int main() {
    double x,y;
    cin>>x;
    if(x>=0 && x<5)y=-x+2.5;
    else if(x>=5 && x<10)y=2-1.5*(x-3)*(x-3);
    else if(x>=10 && x<20)y=x/2-1.5;
    printf("%0.3f",y);
}