8243. The first digit of the number

Find the first digit of an integer. Start count digits from the leftmost one.

Input. One 64-bit integer containing at least one digits. The number can be negative.

Output. Print the first digit of a given integer.

Sample input 1	Sample output 1
1234567890123	1
Sample input 2	Sample output 2
-7654321	7

SOLUTION

loop

Algorithm analysis

If number is negative, then change its sign, making it positive – this will not change the first digit. Divide number by 10 until one digit remains in it – this will be the first digit of the original number.

Algorithm realization

Read the input value of n.

scanf("%lld",&n);

If the number is negative, then make it positive.

if (n < 0) n = -n;

Divide number by 10 until it contains only the first digit.

while(n > 9)

n /= 10;

Print the first digit of number.

printf("%lld\n",n);

Java realization

import java.util.*;

public class Main

{

public static void main(String[] args)

{

Scanner con = new Scanner(System.in);

long n = con.nextLong();

if (n < 0) n = -n;

while(n > 9)

n /= 10;

System.out.println(n);

con.close();

}

}