#include"cstdio"
int k;
int main(){
//1,1,2,3,5,8,13,21……
scanf("%d",&k);
switch(k){
case 1:printf("1");break;
case 2:printf("1");break;
case 3:printf("2");break;
case 4:printf("3");break;
case 5:printf("5");break;
case 6:printf("8");break;
case 7:printf("13");break;
case 8:printf("21");break;
case 9:printf("34");break;
case 10:printf("55");break;
case 11:printf("89");break;
case 12:printf("144");break;
case 13:printf("233");break;
case 14:printf("377");break;
case 15:printf("610");break;
case 16:printf("987");break;
case 17:printf("1597");break;
case 18:printf("2584");break;
case 19:printf("4181");break;
case 20:printf("6765");break;
}
}
