백준 7단계 no.4

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String s = br.readLine();
        br.close();

        StringTokenizer st = new StringTokenizer(s," ");
        double a = Integer.parseInt(st.nextToken());
        double b = Integer.parseInt(st.nextToken());
        double v = Integer.parseInt(st.nextToken());

        int yesterday = (int) Math.ceil((v-a)/(a-b));

        System.out.println(yesterday+1);
    }
}

틀린 이유 : 시간 제한 간과