Language: Java

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/*
 * Copyright (c) --> Arpit
 * Date Created : 13/9/2020
 * Have A Good Day !
 */

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Arpit
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader in = new FastReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        DRedistribution solver = new DRedistribution();
        solver.solve(1, in, out);
        out.close();
    }
    
    static class DRedistribution {
        long mod = (long) 1e9 + 7;
        long dp;
        
        long REC(long sum) {
            if (dp[(int) sum] != -1) return dp[(int) sum];
            if (sum == 0) return 1;
            else if (sum < 3) return 0;
            long curr_ans = 0;
            for (int i = 3; i <= sum; i++) curr_ans = (curr_ans + REC((sum - i))) % mod;
            return dp[(int) sum] = curr_ans;
        }
        
        public void solve(int testNumber, FastReader r, OutputWriter out) {
            long s = r.nextLong();
            dp = new long[2001];
            Arrays.fill(dp, -1);
            long ans = REC(s);
            out.println(ans);
        }
        
    }
    
    static class OutputWriter {
        private final PrintWriter writer;
        
        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }
        
        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }
        
        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                writer.print(objects[i]);
                if (i != objects.length - 1) writer.print(" ");
            }
        }
        
        public void println(Object... objects) {
            print(objects);
            writer.println();
        }
        
        public void close() {
            writer.close();
        }
        
    }
    
    static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private FastReader.SpaceCharFilter filter;
        
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        
        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }
        
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
        
        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }
        
        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
            
        }
        
    }
}



Compiler output:
Main.java:42: error: array required, but long found
            if (dp[(int) sum] != -1) return dp[(int) sum];
                  ^
Main.java:42: error: array required, but long found
            if (dp[(int) sum] != -1) return dp[(int) sum];
                                              ^
Main.java:47: error: array required, but long found
            return dp[(int) sum] = curr_ans;
                     ^
Main.java:52: error: incompatible types: long[] cannot be converted to long
            dp = new long[2001];
                 ^
Main.java:53: error: no suitable method found for fill(long,int)
            Arrays.fill(dp, -1);
                  ^
    method Arrays.fill(long[],long) is not applicable
      (argument mismatch; long cannot be converted to long[])
    method Arrays.fill(int[],int) is not applicable
      (argument mismatch; long cannot be converted to int[])
    method Arrays.fill(short[],short) is not applicable
      (argument mismatch; long cannot be converted to short[])
    method Arrays.fill(char[],char) is not applicable
      (argument mismatch; long cannot be converted to char[])
    method Arrays.fill(byte[],byte) is not applicable
      (argument mismatch; long cannot be converted to byte[])
    method Arrays.fill(boolean[],boolean) is not applicable
      (argument mismatch; long cannot be converted to boolean[])
    method Arrays.fill(double[],double) is not applicable
      (argument mismatch; long cannot be converted to double[])
    method Arrays.fill(float[],float) is not applicable
      (argument mismatch; long cannot be converted to float[])
    method Arrays.fill(Object[],Object) is not applicable
      (argument mismatch; long cannot be converted to Object[])
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
5 errors