#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 age(int m){ if(m==0)return 0; else if(m==1||m==2)return 1; else return age(m-1)+age(m-2); int main(){ int n; cin>>n; cout<<age(n)<<endl; //cout<<abs(-5)<<endl; //cout<<fabs(-1.5)<<endl; //cout<<min('a','c')<<endl; //cout<<max(max('a','c'),'m')<<endl; //cout<<round(4.586)<<endl; //cout<<round(4.586*100)/100.0<<endl; //cout<<pow(4.0,2)<<endl; //cout<<sqrt(4.0)<<endl; return 0; }