#include <stdio.h>

int main()
{
    float luggage_weight;
    float shipping_fee;
    scanf("%f", &luggage_weight);
    if (luggage_weight <= 10.0)
    {
        shipping_fee = luggage_weight * 1.5;
    }
    else
    {
        shipping_fee = 10.0 * 1.5 + (luggage_weight - 10.0) * 2.5;
    }
    printf("托运费：%.2f 元\n", shipping_fee);

    return 0;
}
/**************************************************************
	Problem: 1041
	User: fuhoubin
	Language: C++
	Result: Wrong Answer
****************************************************************/