#include<bits/stdc++.h>
using namespace std;
int main()
{
    double c , a = 2.50;
    cin >> c;
    if(c <= 10)
    {
        printf("%.2f",a);
    }
    else
    {
        c = c - 10;
        c = c * 1.50;
        a = c + a;
        printf("%.2f",a);
    }
    return 0;
}

A

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

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
	float x,n;
	cin >> n;
	if (n <= 10)
    {
		x = 2.5;
	}
    if (n > 10)
    {
		x = 2.5 + (n - 10) * 1.5;
	}
	cout << fixed << setprecision(2) << x << endl;
    return 0;
}

//什么是赞？哪位大佬可以点给我看一下？求求了❤️

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin >> n;
    if(n <= 10)
    {
        cout << fixed << setprecision(2) << 2.5;
    }
    if(n > 10)
    {
        cout << fixed << setprecision(2) << (n - 10) * 1.5 + 2.5;
    }
    return 0;

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int x;
    cin>>x;
    if (x<=10)
        cout<<fixed<<setprecision(2)<<2.5;
    else
        cout<<fixed<<setprecision(2)<<1.5*(x-10)+2.5;
    return 0;
}

号没了

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