Submission #3247057

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Source Code Expand

import java.io.IOException;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
    static final int INF = 10007;
    public static void main(String[] args) throws IOException {
        try (
            BufferedReader reader = new BufferedReader(
                new InputStreamReader(System.in))) {
            final String s = reader.readLine();

            int n = Integer.parseInt(s);

            System.out.println(getTribonacci(n));
        }
    }

    static int getTribonacci(int n) {
        int a1 = 0;
        int a2 = 0;
        int a3 = 1;

        if (n == 1) return a1;
        if (n == 2) return a2;
        if (n == 3) return a3;

        int an = 0;
        for (int i = 4; i <= n; i++) {
            an = modadd(modadd(a1, a2), a3);
            a1 = a2;
            a2 = a3;
            a3 = an;
        }

        return an;
    }

    // aとbを足した値をmodする(a + b mod p)
    static int modadd(int a, int b)
    {
        return (a + b) % INF;
    }
}

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