求指导(细致)，必关注

#include<bits/stdc++.h>
using namespace std;
int main(){
	long long int k,a,b,c;
	cin>>k>>a>>b>>c;
	long long int sum=0,sum1=0,sum2=0,sum3=0,sum4=0,cnt=0;
	for(int i=1;i<=k;i++){
		int t;
		cin>>t;
		if(t<=10){
			sum=sum+10*a;
		}
		else if(t>10 and t<100){
			sum1=t-10;
			sum2=sum1*b;
			sum4=10*a+sum2;
			sum=sum+sum4;
		}
		else if(t>=100){
			sum1=t-10;
			sum2=sum1-90;
			sum3=sum2*c;
			sum4=10*a+90*b+sum3;
			sum=sum+sum4;
		}
	}
	cout<<sum-10*a;
	return 0;
}