#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 x; cin>>x; if(x<=2) cout<<6; if(x<=10&&x>2){ cout<<6+(x-2)*1.8; } if(x>10) cout<<6+8*1.8+(x-10)*1.8*1.5; return 0; }