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#define _GNU_SOURCE
#include <math.h>

double exp10(double x)
{
	static const double p10[] = {
		1e-15, 1e-14, 1e-13, 1e-12, 1e-11, 1e-10,
		1e-9, 1e-8, 1e-7, 1e-6, 1e-5, 1e-4, 1e-3, 1e-2, 1e-1,
		1, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
		1e10, 1e11, 1e12, 1e13, 1e14, 1e15
	};
	double n, y = modf(x, &n);
	if (fabs(n) < 16) {
		if (!y) return p10[(int)n+15];
		y = exp2(3.32192809488736234787031942948939 * y);
		return y * p10[(int)n+15];
	}
	return pow(10.0, x);
}