#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,b,c; cin>>a; if(a<=2){ b=6; } else if(a>=2){ b=6+(a-2)*0.5; } else{ b=6+(10-2)*1.8+(a-10)*1.8*1.5; } cout<<b; return 0; }