#include <stdio.h>
#include <stdlib.h>

unsigned int convertInt(char *s, unsigned int *r) {
  long int     bigValue ;
  unsigned int retValue ;
  char        *test ;
  bigValue = strtol(s, &test, 10) ;
  retValue = bigValue ;
  if (*s == '\0' || *test != '\0' || retValue != bigValue) {
    return 0 ;
  } else {
    *r = retValue ;
    return 1 ;
  }
}

int main(int argc, char *argv[]) {
  unsigned int m, n ;
  if (argc==3) {
    int badArg = 0 ;
    if (! convertInt(argv[1], &m)) {
      printf("Invalid argument: %s\n", argv[1]) ;
      badArg = 1 ;
    }
    if (! convertInt(argv[2], &n)) {
      printf("Invalid argument: %s\n", argv[2]) ;
      badArg = 1 ;
    }
    if (badArg) {
      return EXIT_FAILURE ;
    } else if (m > n) {
      printf("First argument (%u) should be smaller than second (%u)\n",
	     m, n) ;
      return EXIT_FAILURE ;
    } else {
      printf("%u! is %lu\n", m, factorial(m)) ;
      printf("comb(%u, %u) is %lu\n", m, n, combinations(m, n)) ;
      printf("perm(%u, %u) is %lu\n", m, n, permutations(m, n)) ;
      return EXIT_SUCCESS ;
    }
  } else {
    printf("Wrong number of arguments\n") ;
    return EXIT_FAILURE ;
  }
}