#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> using namespace std; int main(){ long long k,a=1,b=1,c,i=2; cin>>k; if(k<=2) { cout<<1; return 0; } while(i<k) { c=a+b; a=b; b=c; i++; } cout<<c; }