UVA - 10323 - Factorial! You Must be Kidding!!!

#include <stdio.h>

int main()
{
        int x;
        long i;
        long long arr[14];
        arr[0]=1;
        for(i=1;i<14;i++){
            arr[i]=arr[i-1]*i;
        }
        while(scanf("%d",&x)==1) {
            if(x<0){
                if(x%2==0){
                  puts("Underflow!");
                }
                else{
                  puts("Overflow!");
                }
            }
            else if(x<8 && x>-1){
                puts("Underflow!");
            }
            else if(x>13){
                puts("Overflow!");
            }
            else{
                printf("%lld\n",arr[x]);
            }
        }

    return 0;
}