/*Fibbonacci Number

Problem Description

Your objective for this question is to develop a program which will generate a fibbonacci number. The fibbonacci function is defined as such:

f(0) = 0

f(1) = 1

f(n) = f(n-1) + f(n-2)

Your program should be able to handle values of n in the range 0 to 50.

Input

Each test case consists of one integer n in a single line where 0≤n≤50. The input is terminated by -1.

Output

Print out the answer in a single line for each test case.

Sample Input

3

4

5

-1

Sample Output

2

3

5

you can use 64bit integer: __int64

*/

#include<cstdio>

#include<string.h>

__int64 s[100]={0,1,0};

int main()

{

    int n,i;

    while(~scanf("%d",&n),n!=-1)

    {

       for(i=2;i<=n;i++)

       {

            s[i]=s[i-1]+s[i-2];

        }

        printf("%I64d\n",s[n]);

    }

    return 0;

}