杭电2070

#include<stdio.h>
long long a[51];
int main()
{
    int n,i;
    a[1]=1;
    for(i=2; i<51; ++i)
        a[i]=a[i-1]+a[i-2];
    while(~scanf("%d",&n) && n!=-1)
        printf("%lld\n",a[n]);
}