AtCoder Beginner Contest 044 A

Time limit : 2sec / Memory limit : 256MB

Score : 100 points

Problem Statement

There is a hotel with the following accommodation fee:

• X yen (the currency of Japan) per night, for the first K nights
• Y yen per night, for the (K+1)-th and subsequent nights

Tak is staying at this hotel for N consecutive nights. Find his total accommodation fee.

Constraints

• 1≤N,K≤10000
• 1≤Y<X≤10000
• N, K, X, Y are integers.

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Input

The input is given from Standard Input in the following format:

N
K
X
Y

Output

Print Tak's total accommodation fee.

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Sample Input 1

Copy

5
3
10000
9000

Sample Output 1

Copy

48000

The accommodation fee is as follows:

• 10000 yen for the 1-st night
• 10000 yen for the 2-nd night
• 10000 yen for the 3-rd night
• 9000 yen for the 4-th night
• 9000 yen for the 5-th night

Thus, the total is 48000 yen.

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Sample Input 2

Copy

2
3
10000
9000

Sample Output 2

Copy

20000

题解：水过

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <map>
#include <set>
#include <queue>
#include <stack>
using namespace std;
#define lowbit(x) (x&(-x))
#define max(x,y) (x>y?x:y)
#define min(x,y) (x<y?x:y)
#define MAX 100000000000000000
#define MOD 1000000007
#define pi acos(-1.0)
#define ei exp(1)
#define PI 3.141592653589793238462
#define INF 0x3f3f3f3f3f
#define mem(a) (memset(a,0,sizeof(a)))
typedef long long ll;
ll gcd(ll a,ll b){
    return b?gcd(b,a%b):a;
}
bool cmp(int x,int y)
{
    return x>y;
}
const int N=10005;
const int mod=1e9+7;
int main()
{
    std::ios::sync_with_stdio(false);
    int n,k,x,y;
    cin>>n>>k>>x>>y;
    ll s=0;
    if(n<=k) s+=n*x;
    else s+=k*x+(n-k)*y;
    cout<<s<<endl;
    return 0;
}