#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 m; double s=0; cin>>m; if(m>10){ s=6+(10-2)*1.8+(m-10)*1.8*1.5; }else{ if(m>10){ s=6+(m-2)*1.8; }else{ s=6; } } cout<<s; return 0; }