#include #define ll long long #define INF 1000000005 #define MOD 1000000007 #define EPS 1e-10 #define rep(i,n) for(int i=0;i<(int)n;++i) #define each(a, b) for(auto (a): (b)) #define all(v) (v).begin(),(v).end() #define fi first #define se second #define pb push_back #define show(x) cout <<#x<<" = "<<(x)<P; const int MAX_N = 100005; int main() { long double a,b,c; cin >> a >> b >> c; long double r = (c - b) / (b - a); long double d = c - r*b; long double hoge = r*c + d; int res = (int)(r*c + d); if(abs(res - hoge) < 0.1){ cout << res << endl; }else if(abs(res+1 - hoge) < 0.1){ cout << res + 1 << endl; }else{ cout << res - 1 << endl; } return 0; }