#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int iters = 100;
double a = 0;
for (int q = 0; q < iters; q++)
for (int i = 1; i < 10000000; i++)
if (i%2 == 0) a*=i; else a /=i;
cout << a;
return 0;
}
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