蒟蒻求助！#2#5

#include<bits/stdc++.h>
using namespace std;
double m;
int main(){
	int a;
	cin>>a;
	if(a<=150)m=a*0.4463;
	else if(a<=400)m=66.945+(a-150)*0.4663;
	else m=66.945+116.575+(a-400)*116.575;
	printf("%.1lf",m);
	return 0;
} 

Why?

Why！