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filename

primes_up_to_10^8.cpp

#include<iostream>⏎
#include <cstring>⏎
⏎
char prime[100000000];⏎
⏎
void Sieve(int64_t n) {⏎
    memset(prime, '1', sizeof(prime));  // intitize '1' to every index⏎
    prime[0] = '0';  // 0 is not prime⏎
    prime[1] = '0';  // 1 is not prime⏎
    for (int p = 2; p * p <= n; p++) {⏎
        if (prime[p] == '1') {⏎
            for (int i = p * p; i <= n; i += p)⏎
                prime[i] = '0';  // set all multiples of p to false⏎
        }⏎
    }⏎
}⏎
⏎
⏎
int main() {⏎
    Sieve(100000000);⏎
    int64_t n;⏎
    std::cin >> n;  // 10006187⏎
    if (prime[n] == '1')⏎
        std::cout << "YES\n";⏎
    else⏎
        std::cout << "NO\n";⏎
}⏎