#include <stdio.h>
int main()
{
	freopen("kfib.in","r",stdin);
	freopen("kfib.out","w",stdout);
	int n,x,y,z,d;
scanf("%d",&n);
x=1;
y=1;
z=1;
for(d=3;d<=n;d++)
{
z=x+y;
x=y;
y=z;
}
printf("%d",z);
return 0;
}