车站题解

#include <iostream>
using namespace std;

int a,n,m,x;
int A[25] = {0,1,1,2,2},K[25] = {0,0,0,0,1};

int main(){
cin >> a >> n >> m >> x;
if (x <= 2){
cout << a;
return 0;
}
for (int i = 4;i <= n-1;++i){
A[i] = A[i-1] + A[i-2] - 1;
K[i] = K[i-1] + K[i-2] + 1;
}

int p = (m - A[n-1] * a) / K[n-1] ;
cout << A[x] * a + K[x] * p;

return 0;

}