I need to combine these programs into one program that works for a positive integer "n"

The first is a sum of squares starting with 1 until "n"

The second is a sum of cubes starting with 1 until "n"

The third is a sum of fractions starting with 1/2^1 until 1/2^n

I know I need to take out my exit stuff until the last one and all I need is one set of preprocessor directives.

Code:

#include <stdio.h>
#include <math.h>
main ()
{
/* Declare variables */
int i, n, sumsquare = 0;;
printf("Enter n: \n");
scanf("%d", & n);
/* Set for loop conditions */
for (i=1; i <= n; i++)
{
sumsquare += i*i;
}
printf ("The sum of the squares from 1..%d is %d\n", n,
sumsquare);
system("pause");
exit(0);
}
{
/* Declare and initialize variables */
int i=0, n, sumcubes=0;
printf("Enter n: \n");
scanf("%i", &n);
/* Set for loop conditions */
while (i++<n)
{
sumcubes += (i*i*i);
}
printf ("The sum of the cubes from 1..%d is %d\n", n,
sumcubes);
system("pause");
exit(0);
}
{
unsigned int i = 1, n;
float sum=0;
printf("Enter n: \n");
scanf("%u", &n);
do
{
sum += (1/(pow(2,i)));
}
while (i++ < n);
printf ("The sum of the fractional exponentials from 1 ... %u is %f\n",
n, sum);
system ("pause");
return 0;
}