Ответ:

#include <iostream>

#include <math.h>

using namespace std;

int main()

{

long double n = 2;

long double P;

int N;

cout << "vvedite N" << endl;

cin >> N;

P = 1;

for(int i = 0; i<N;i++){

P = P * (1-(1/(pow(n,2))));

n++;

}

cout << P << endl;

return 0;

}