#include using namespace std; typedef long long ll; typedef vector vint; typedef pair pint; typedef vector vpint; #define rep(i,n) for(int i=0;i<(n);i++) #define REP(i,n) for(int i=n-1;i>=(0);i--) #define reps(i,f,n) for(int i=(f);i<(n);i++) #define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++) #define all(v) (v).begin(),(v).end() #define eall(v) unique(all(v), v.end()) #define pb push_back #define mp make_pair #define fi first #define se second #define chmax(a, b) a = (((a)<(b)) ? (b) : (a)) #define chmin(a, b) a = (((a)>(b)) ? (b) : (a)) const int MOD = 1e9 + 7; const int INF = 1e9; const ll INFF = 1e18; ll b1, b2, b3; int main(void) { cin >> b1 >> b2 >> b3; double r = (double)(b3 - b2) / (b2 - b1); // printf("%lf\n", r); double d = b2 - r * b1; double ans = r * b3 + d; printf("%lld\n", (ll)ans); return 0; }