Since n \le 10^{13}, storing all values A_i~(i = 0, 1, ..., n) is impossible, either using an array or a map structure due to memory limitations. Therefore, we’ll use recursion defined by the recurrence relation for computations.
At the same time, the values A_i for i < 5000000 will be stored in the array to avoid repeated computations and speed up the program.
Algorithm implementation
To store the values A_i~(i < 5000000), declare an array .
#define MAX 5000000
long long m[MAX];The function f computes the value of A_n.
long long f(long long n, long long p, long long q,
long long x, long long y)
{If n \le 0, then A_n = 1.
if (n <= 0) return 1;If n < 5000000 and the value is already computed (is not zero), return it.
if ((n < MAX) && m[n]) return m[n];Perform a recursive computation of A_n according to the formula provided in the problem statement.
long long temp = f(n/p-x,p,q,x,y) + f(n/q-y,p,q,x,y);If n < 5000000, store the result A_n in the array to avoid repeated computations in the future.
if (n < MAX) m[n] = temp;
return temp;
}The main part of the program. Read the input data.
scanf("%lld %lld %lld %lld %lld",&n,&p,&q,&x,&y);Compute and print the answer.
res = f(n,p,q,x,y);
printf("%lld\n",res);Java implementation
import java.util.*;
public class Main
{
static int MAX = 5000000;
static long m[] = new long[MAX];
public static long f(long n, long p, long q, long x, long y)
{
if (n <= 0) return 1;
if (n < MAX && m[(int)n] > 0) return m[(int)n];
long temp = f(n/p-x,p,q,x,y) + f(n/q-y,p,q,x,y);
if (n < MAX) m[(int)n] = temp;
return temp;
}
public static void main(String[] args)
{
Scanner con = new Scanner(System.in);
long n = con.nextLong();
long p = con.nextLong();
long q = con.nextLong();
long x = con.nextLong();
long y = con.nextLong();
long res = f(n,p,q,x,y);
System.out.println(res);
con.close();
}
}Python implementation
To store the values A_i~(i < 5000000), declare a list .
MAX = 5000000
m = [0] * MAXThe function f computes the value of A_n.
def f(n, p, q, x, y):If n \le 0, then A_n = 1.
if n <= 0:
return 1If n < 5000000 and the value is already computed (is not zero), return it.
if n < MAX and m[n]:
return m[n]Perform a recursive computation of A_n according to the formula provided in the problem statement.
temp = f(n // p - x, p, q, x, y) + f(n // q - y, p, q, x, y)If n < 5000000, store the result A_n in the array to avoid repeated computations in the future.
if n < MAX: m[n] = temp
return tempThe main part of the program. Read the input data.
n, p, q, x, y = map(int, input().split())Compute and print the answer.
res = f(n, p, q, x, y)
print(res)