一定要考虑重量为整数的时候，这个写着写着就遗忘了 
#include<iostream>
#include<iomanip>

using namespace std;
int main()
{
    float weight;
    int weight1,price,extraprice;
    char cha;
    cin>>weight>>cha;
    weight1=weight;
    if(cha=='y')
    {
        if(weight!=weight1&&weight>0)
        {
            cout<<int(weight1)+25;
        } 
        else cout<<int(weight1-1)+25;
    }
    if(cha=='n')
    {
        if(weight!=weight1&&weight>0)
        {
            cout<<int(weight1)+20;
        } 
        else cout<<int(weight1-1)+20;
    }
    return 0;
}