UVA - 10918 - Tri Tiling (C Solution)

#include <stdio.h>

int main()
{
    int x,i;
    long arr[31];
    long arr2[31];
    arr[0] = arr2[1] = 1;
    arr[1] = arr2[0] = 0;
    for (i = 2; i < 31; i++) {
            arr[i] = arr[i - 2] + 2 * arr2[i - 1];
            arr2[i] = arr[i - 1] + arr2[i - 2];
        }
    while(1){
        scanf("%d",&x);
        if(x<0){
            break;
        }
        if(x%2==1){
            puts("0");
        }else{
            printf("%ld\n",arr[x]+arr2[x]);
        }
    }
    return 0;
}