#include<stdio.h>

int k,n,i,j,A[1000],B[1000],C[1000],t;

int main(){


FILE *f=fopen("nunta.in","r");
FILE *g=fopen("nunta.out","w");
fscanf(f,"%d",&n);
fclose(f);

if(n==1||n==2){

  if(n==2)fprintf(g,"%d",2);
  if(n==1)fprintf(g,"%d",1);
}

else{


A[0]=1;
A[1]=1;
B[0]=1;
B[1]=2;

 for(j=3;j<=n;j++){
    k=0;
	 for (i=1; i<=A[0] || i<=B[0] || t; i++, t/=10)
	 { k++; C[i] = (t += A[i] + B[i]) % 10; }

      C[0] = k ;


   for(i=0;i<=B[0];i++){
   A[i]=B[i];
   }

   for(i=0;i<=C[0];i++){
   B[i]=C[i];
   }



   for(i=1;i<=C[0];i++){
   C[i]=0;
   }
   C[0]=0;

 }




for(i=B[0];i>=1;i--){
fprintf(g,"%d",B[i]);
}
}

fclose(g);


return 0;
}