#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int a=1,b=1,c=1,d,i; cin>>d; for(i=3;i<=d;i++){ c=a+b; a=b; b=c; } cout<<c; return 0; }