#include using namespace std; int p(string S,int i,int count){ if(S.size()==i)return 1; if(S.at(i)=='0'){count/=4;return p(S,i+1,count);} if(S.at(i)=='3'){count/=(i==0? 3:4);return p(S,i+1,count)+count;} if(S.at(i)=='6'){count/=(i==0? 3:4);return p(S,i+1,count)+count*2;} if(S.at(i)=='9'){count/=(i==0? 3:4);return p(S,i+1,count)+count*3;} if(S.at(i)<'3')return count/(i==0? 3:4); if(S.at(i)<'6')return count/(i==0? 3:4)*2; if(S.at(i)<'9')return count/(i==0? 3:4)*3; } int main(){ int N;cin>>N; if(N<100){ cout<<(N-9)/3<