Given a number, the task is that we divide number by 3. The input number may be large and it may not be possible to store even if we use long long int.

Examples:

Input : n = 769452 Output : Yes Input : n = 123456758933312 Output : No Input : n = 3635883959606670431112222 Output : Yes

Since input number may be very large, we cannot use n % 3 to check if a number is divisible by 3 or not, especially in languages like C/C++. The idea is based on following fact.

A number is divisible by 3 if sum of its digits is divisible by 3.

**Illustration:**

For example n = 1332 Sum of digits = 1 + 3 + 3 + 2 = 9 Since sum is divisible by 3, answer is Yes.

**How does this work?**

Let us consider 1332, we can write it as 1332 = 1*1000 + 3*100 + 3*10 + 2 The proof is based on below observation: Remainder of 10^{i}divided by 3 is 1 So powers of 10 only result in value 1. Remainder of "1*1000 + 3*100 + 3*10 + 2" divided by 3 can be written as : 1*1 + 3*1 + 3*1 + 2 = 9 The above expression is basically sum of all digits. Since 9 is divisible by 3, answer is yes.

Below is the implementation of above fact :

## C++

// C++ program to find if a number is divisible by // 3 or not #include<bits/stdc++.h> using namespace std; // Function to find that number divisble by 3 or not int check(string str) { // Compute sum of digits int n = str.length(); int digitSum = 0; for (int i=0; i<n; i++) digitSum += (str[i]-'0'); // Check if sum of digits is divisible by 3. return (digitSum % 3 == 0); } // Driver code int main() { string str = "1332"; check(str)? cout << "Yes" : cout << "No "; return 0; }

## Java

// Java program to find if a number is // divisible by 3 or not class IsDivisible { // Function to find that number // divisble by 3 or not static boolean check(String str) { // Compute sum of digits int n = str.length(); int digitSum = 0; for (int i=0; i<n; i++) digitSum += (str.charAt(i)-'0'); // Check if sum of digits is // divisible by 3. return (digitSum % 3 == 0); } // main function public static void main (String[] args) { String str = "1332"; if(check(str)) System.out.println("Yes"); else System.out.println("No"); } }

## Python

# Python program to find if a number is # divisible by 3 or not # Function to find that number # divisble by 3 or not def check(num) : # Compute sum of digits digitSum = 0 while num > 0 : rem = num % 10 digitSum = digitSum + rem num = num / 10 # Check if sum of digits is # divisible by 3. return (digitSum % 3 == 0) # main function num = 1332 if(check(num)) : print "Yes" else : print "No" # This code is contributed by Nikita Tiwari.

Output:

Yes

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