#include <stdio.h>
int main()
{int v1[3000],v2[3000],v3[3000],nv1,nv2,max,r,n,i,j;

freopen("nunta.in","r",stdin);
freopen("nunta.out","w",stdout);
scanf("%d",&n);
v1[1]=0;nv1=1;
v2[1]=1;nv2=1;
for (i=1;i<=n;i++)
{ r=0;if (nv1>=nv2) max=nv1; else max=nv2;  //printf("%d ",v1[1]); printf("%d \n",v2[1]);
  for (j=1;j<=max;j++) 
	{v3[j]=v1[j]+v2[j]+r;r=v3[j]/10;v3[j]=v3[j]%10;}
  for(;r!=0;) {max++;v3[max]=r;r=v3[max]/10;v3[max]=v3[max]%10;} 
  
  for (j=1;j<=nv2;j++)  v1[j]=v2[j]; nv1=nv2;
  for (j=1;j<=max;j++)  v2[j]=v3[j];nv2=max;
 
  /*for (j=nv2;j>=1;j--) printf("%d ",v2[j]);*/
    
}
 for (i=nv2;i>=1;i--) printf("%d",v2[i]);
return 0;}