#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
	double n;
	cin >> n;
	if (n <= 15)
	{
		cout << fixed << setprecision(2) << n/1.5;
	}
	if (n > 15)
	{
		cout << fixed << setprecision(2) << (n + 10) / 2.5;
	}
	return 0;
}

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
    double n;
    cin >> n;
    if(n > 15)
    {
        cout << fixed << setprecision(2) << 10 + (n - 15) / 2.5;
    }
    else
    {
        cout << fixed << setprecision(2) << n / 1.5;
    }
    return 0;
}已AC

#include<bits/stdc++.h>
using namespace std;
int main()
{
    double x;
    cin>>x;
    if (x<=15)//这里注意不是10
        cout<<fixed<<setprecision(2)<<x/1.5;
    else
        cout<<fixed<<setprecision(2)<<10+(x-15)/2.5;//10和15不要写反
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    double a,b,c;
    cin>>a;
    b=a/1.5;
    if(b>10)
    {
        b=10;
        c=a-15;
        printf("%.2f",b+c/2.5);
        return 0;
    }
    printf("%.2f",b);
    return 0;
}

号没了

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    if(n<=10)
    {
        cout << fixed << setprecision(2) << n/1.5;
    }
    else
    {
        cout << fixed << setprecision(2) << (n-15)/2.5+10;
    }
}