Educational Codeforces Round 15 D Road to Post Office（分类讨论）

思路：由于车的速度肯定大于人的，那么第一段肯定是开车最优，然后分三种情况讨论，分别是剩下的都走路，一直开车到最后一段<k的时候走路，或者全程开车

#include<bits/stdc++.h> using namespace std; #define LL long long LL d,k,a,b,t; int main() { LL ans = 0; scanf("%lld%lld%lld%lld%lld",&d,&k,&a,&b,&t); LL last = d-k; if(last<=0)printf("%lld\n",d*a); else { d = last; ans+=k*a; LL t1 = d*b; //剩下的路程全部走路 LL t2 = (d/k)*k*a+(d/k)*t+(d-(d/k)*k)*b; //剩下的路程开车到小于k走路 LL t3 = d*a+((d/k)+1)*t; //一直开车 ans+=min(t1,min(t2,t3)); printf("%lld\n",ans); } }

D. Road to Post Office time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output

Vasiliy has a car and he wants to get from home to the post office. The distance which he needs to pass equals to d kilometers.

Vasiliy's car is not new — it breaks after driven every k kilometers and Vasiliy needs t seconds to repair it. After repairing his car Vasiliy can drive again (but after k kilometers it will break again, and so on). In the beginning of the trip the car is just from repair station.

To drive one kilometer on car Vasiliy spends a seconds, to walk one kilometer on foot he needs b seconds (a < b).

Your task is to find minimal time after which Vasiliy will be able to reach the post office. Consider that in every moment of time Vasiliy can left his car and start to go on foot.

Input

The first line contains 5 positive integers d, k, a, b, t (1 ≤ d ≤ 10¹²; 1 ≤ k, a, b, t ≤ 10⁶; a < b), where:

d — the distance from home to the post office; k — the distance, which car is able to drive before breaking; a — the time, which Vasiliy spends to drive 1 kilometer on his car; b — the time, which Vasiliy spends to walk 1 kilometer on foot; t — the time, which Vasiliy spends to repair his car. Output

Print the minimal time after which Vasiliy will be able to reach the post office.

Examples Input 5 2 1 4 10 Output 14 Input 5 2 1 4 5 Output 13 Note

In the first example Vasiliy needs to drive the first 2 kilometers on the car (in 2 seconds) and then to walk on foot 3 kilometers (in 12 seconds). So the answer equals to 14 seconds.

In the second example Vasiliy needs to drive the first 2 kilometers on the car (in 2 seconds), then repair his car (in 5 seconds) and drive 2 kilometers more on the car (in 2 seconds). After that he needs to walk on foot 1 kilometer (in 4 seconds). So the answer equals to 13 seconds.