Function To Find Factorials!!! Please Help

i need to write a function to find factorials of numbers the catch is i can only use + or - for and while loops..

eg 5! = 5 x 4 x 3 x 2 x 1 = 120

i cannot use any * in it;

this is what i have so far

the factorial has been entered in another function and is passed to this one

void find_factorials(int factorial)

{

int count = 0;

int answer = 0;

int i = 1;

int n = factorial;

for(n = factorial ; n>0 ;n--)

{

for(count = factorial - i; count >0; count--)

{

answer = answer + factorial;

}

i++ ;

}

}

can someone please help me thanks heeps :)