int main(void) {
int i, result;
int *data;
scanf("%d", &n);
data = (int *)malloc(sizeof(int)*n);
half = 0;
for (i=0; i<n; i++) {
scanf("%d", (data+i));
half += *(data+i);
}
if (half%2 != 0) {
printf("impossible\n");
free(data);
return 0;
}
// sort
merge_sort(data);
half /= 2;
cnt = 0;
// find (backtracking)
findAvailable(data, 0, 0);
if (cnt == 0) printf("impossible\n");
else printf("%d\n", cnt);
free(data);
return 0;
}
void findAvailable(int *data, int sum, int idx) {
int i;
for (i=idx; i<n; i++) {
if (sum+data[i] > half) break;
else if (sum+data[i] == half) cnt++;
else findAvailable(data, sum+data[i], i+1);
}
}
char *stringMemory::allocate(size_t size) {
assert(m_head);
if (size == 0)
return allocate(1);
const size_t totalSize = getSize(size);
region *available = findAvailable(totalSize);
if (available) {
available->setFree(false);
return (char *)(available + 1);
} else {
// Merge free blocks until they're all merged
while (mergeFree())
;
// Now try and find a free block
available = findAvailable(totalSize);
// Got a free block
if (available) {
available->setFree(false);
return (char *)(available + 1);
}
}
abort();
}
