#include <stdio.h>
int a[10000],b[10000],c[10000];
void adunare()  
{  
	int i, t = 0;
	for (i=1; i<=a[0] || i<=b[0] || t; i++, t/=10)  
		c[i] = (t += a[i] + b[i]) % 10;  
	c[0] = i - 1;  
}  
int main()
{
	FILE *in,*out;
	int n,i,j;
	in=fopen("nunta.in","r");
	out=fopen("nunta.out","w");
	fscanf(in,"%d",&n);
	if (n==1)
	{
		fprintf(out,"1\n");
		fclose(in);
		fclose(out);
		return 0;
	}
	if (n==2)
	{
		fprintf(out,"2\n");
		fclose(in);
		fclose(out);
		return 0;
	}
	a[0]=1;
	a[1]=1;
	b[0]=1;
	b[1]=2;
	for (i=3;i<=n;i++)
	{
		adunare();
		for (j=0;j<=b[0];j++)
			a[j]=b[j];
		for (j=0;j<=c[0];j++)
			b[j]=c[j];
	}
	for (i=b[0];i>=1;i--)
		fprintf(out,"%d",b[i]);
	fprintf(out,"\n");
	fclose(in);
	fclose(out);
	return 0;
		
}