How can I use nested loop to solve the problem below?

Calculate the valuse of x from the infinite series

x=4- 4/3 + 4/5 - 4/7 + 4/9 - 4/11 + .......

Print a table that shows the value of x approximated by 1,2,3,etc, terms.

What I wrote is:

#include <iostream.h>

#include <iomanip.h>

#include <math.h>

void print(double x,int n)

{

cout << (long int) (x) << '.';

for( ; n>0; n--)

{

x = x - (long int) (x);

x = 10. * x;

cout << int(x);

}

}

double dec(double x, int n)

{

double p;

p = pow(10.,n);

return ((long int)(x*p + ((x>0.) ? 0.499999 : -0.499999)))/p;

}

int main()

{

int n;

double f, x = 3.141515151515;

for (cout<< '\n', n=0; n<15; n++)

{cout << '\n' ;print(x, n); }

cout << '\n';

return 0;

}

However, my teacher said that it's completely wrong! So, can anyone tells me how to do the problem by using nested loop?

thank you very much!!