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#include <stdio.h>
unsigned long factorial_rec(unsigned int n)
{
if (n==0) { return 1; }
else { return (unsigned long) n * factorial_rec(n - 1); }
}
int main(void) {
unsigned int n;
printf("Podaj n: ");
if (!scanf("%d", &n))
{
printf("incorrect input");
return -1;
}
else if(n>20)
{
printf("Incorrect input data");
return -2;
} else
printf("%lu", factorial_rec(n));
return 0;
}
