看看哪错了，运行出错，我感觉没错啊

#include<stdio.h>
#define N 10
int main()
{
int arr[N];
int n,a;
arr[1]=1;
arr[2]=2;
while(scanf("%d",&n)!=0)
{
for(a=3;a<=n;a++)
{
arr[a]=arr[a-1]+arr[a-2];
}
printf("%d",arr[n]);
printf("\n");
}
return 0;
}

1 <= N <= 40