#include<stdio.h>
int main(){
      int n;
      int a,b,c,i,num;
    while(~scanf("%d",&n)){
    int a=1,b=1,c=1,num=0;
  
         if(n<=3){
           
         printf("1\n");
       
        }
        if(n>3) {
              for(i=4;i<=n;i++){
                  num=a+c;
                  a=b;
                  b=c;
                  c=num;
                  }
            printf("%d\n",num);
  
        }     
        
    }
    
    return 0;
}