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Suppose we have a number n. We have to find the product of prime numbers between 1 to n. So if n = 7, then output will be 210, as 2 * 3 * 5 * 7 = 210.

We will use the Sieve of Eratosthenes method to find all primes. Then calculate the product of them.

#include<iostream> using namespace std; long PrimeProds(int n) { bool prime[n + 1]; for(int i = 0; i<=n; i++){ prime[i] = true; } for (int i = 2; i * i <= n; i++) { if (prime[i] == true) { for (int j = i * 2; j <= n; j += i) prime[j] = false; } } long product = 1; for (int i = 2; i <= n; i++) if (prime[i]) product *= i; return product; } int main() { int n = 8; cout << "Product of primes up to " << n << " is: " << PrimeProds(n); }

Product of primes up to 8 is: 210

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