Find amicable numbers in C

amicable.c

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

long sumod(long x) {
	long i, s = 1;
	for (i=2; i<=(x/2); i++)
		if ((int)x%i==0)
			s += i;
	return s;
}

int main() {
	const long L = LONG_MAX;
	// Warning, if the program crashes, use a minor value of L (like 9999999) :
	//const long L = 9999999;
	long* cache = malloc(L*sizeof(long));
	long* jvalues = malloc(L*sizeof(long));
	if (cache==NULL || jvalues==NULL) {
		printf("\nError while initializing memory.\n");
		exit(-1);
	}
	long x;
	for (x=0; x<L; x++) {
		cache[x] = 0;
		jvalues[x] = 0;
	}
	for (x=1; x<L; x++) {
		if (!cache[x]) cache[x] = sumod(x);
		if (!cache[cache[x]]) cache[cache[x]] = sumod(cache[x]);
		if (cache[cache[x]]==x && jvalues[x]==0) {
			jvalues[x] = cache[x];
			jvalues[cache[x]] = x;
			printf("%ld, %ld\n", x, cache[x]);
			fflush(stdout);
		}
	}
}