Timus Problem 1086. Cryptography Accepted Solution in C

#include <stdio.h>
#include <math.h>
#include <stdlib.h>

int main()
{
    int i, j, k, n, count, square_root, current_number;
    char is_prime[163842];
    int prime_numbers[15001];

    square_root = (int)sqrt(163841); // 163841 is the 1500th prime number

    for(i = 2; i <= 163841; i++) is_prime[i] = '1';

    for(i = 2; i <= square_root; i++)
    {
        if(is_prime[i] == '1')
        {
            current_number = i * i;

            while(current_number <= 163841)
            {
                is_prime[current_number] = '0';
                current_number += i;
            }
        }
    }

    prime_numbers[1] = 2;

    for(j = 2, i = 3; i <= 163841; i += 2)
    {
        if(is_prime[i] == '1')
        {
            prime_numbers[j] = i;
            j++;
        }
    }

    scanf("%d", &k);

    while(k--)
    {
        scanf("%d", &n);
        printf("%d\n", prime_numbers[n]);
    }

    return 0;
}