#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(){ long long fib=1,f1=1,f2=1,n; cin>>n; for(int i=3;i<=n;i++){ fib=f1+f2; f2=f1; f1=fib; } cout<<fib; return 0; }