#include<stdio.h>
#include<stdlib.h>


int main()
{long k,x=0,y=1;
freopen("kfib.in","r",stdin);
freopen("kfib.out","w",stdout);
scanf("%li",&k);
for(int i=1;i<=k;i++)
{
y=x+y;
x=y-x;
}
printf("%li",x);
return 0;
}