#include using namespace std; using ll = long long; #define FOR(i,a,b) for(ll i=(a);i<(b);++i) #define ALL(v) (v).begin(), (v).end() #define p(s) cout<<(s)<> b1 >> b2 >> b3; ll a = b3*(b3-b1) + b2*(b2-b3); ll b = b2 - b1; p(a/b); return 0; }