/*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;
}