#include <bits/stdc++.h>
using namespace std;
const double eps = 0.001;
int main () {
double a = 1;
double b = 4;
double c;
int N = 4;
double y1, y2;
double F[N];
for (int i = 2; i <= N; i++)
{
F[0] = 1;
F[1] = 1;
F[i] = F[i-2] + F[i-1];
}
double x1;
double x2;
double s1 = 0;
int count = 0;
x1 = a + (b - a) * (F[N-2]/F[N]);
x2 = a + (b - a) * (F[N-1]/F[N]);
y1 = (x1-1)/(x1+1);
y2 = (x2-1)/(x2+1);
do {
if (y1 < y2) {
s1 = b;
b = x2;
y2 = y1;
x2 = x1;
x1 = a + (b - x2);
y1 = (x1-1)/(x1+1);}
else {
s1 = a;
a = x1;
x1 = x2;
x2 = b - (x1 - a);
y1 = y2;
y2 = (x2-1)/(x2+1);}
count++;
c = abs(x1-x2);
}
while (c > eps);
cout << (x1 + x2)/ 2 << endl;
return 0;
}
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