#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
 
int main()
{
    vector<double> v {1.2, 6.0, 66.3, 9.1, 5.5, -0.5, 2.2, 7.8, 2.2};
    auto first_negative = begin(v);
	while (*first_negative > 0.0 && first_negative != end(v))
		++first_negative;
	double geometric_mean =
		pow(accumulate(begin(v), first_negative, 1.0, multiplies<double>()),
			1.0 / static_cast<double>( distance( begin(v), first_negative ) ));
	cout << geometric_mean;
    return 0;
}

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