#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 y,s,e; double p; cin>>y>>s>>e; p=(y+s+e)*1.0/3; printf("%.21f",p); return 0; }