#include<cstdio>
using namespace std;
FILE *f,*g;
int n,i,j,t,y,p,k,m,a[250],b[250],c[250];
int main()
{f=fopen("nunta.in","r");
g=fopen("nunta.out","w");
fscanf(f,"%d",&n);
a[1]=1;
b[1]=1;
m=1;
p=1;
for(i=1;i<n;++i)
{t=0;
for(j=1;j<=p;++j)
{y=a[j]+b[j]+t;
t=y/10;
c[j]=y%10;
}
k=p;
if(t!=0)
{++k;
c[k]=t;
t=0;
}
for(j=1;j<=p;++j)
	a[j]=b[j];
m=p;
for(j=1;j<=k;++j)
	b[j]=c[j];
p=k;
}
if(n==1)
	fprintf(g,"1");
else
	if(n==2)
		fprintf(g,"2");
	else
		if(n==3)
			fprintf(g,"3");
else
for(i=p;i>=1;--i)
	fprintf(g,"%d",c[i]);
fprintf(g,"\n");
return 0;	
}