#include<stdio.h>
int main()
{
int m;
double i=1, s=0;
for (m = 1; m <= 10; ) {
if (m % 2 == 1) {
s = s + i;
m = m + 1;
i = (1.0) / (2 * m - 1);
}
else {
s = s + i;
m = m + 1;
i = (1.0) / (2*m - 1) * (-1);
}
}
printf("%lf", s);
return 0;
}