http://codeforces.com/problemset/problem/317/A

题意：给两个数字，可以两数相加去替换其中一个数字。问要做多少次，可以让两个数字钟至少一个 >= 目标数字m，输出次数，不可能的话输出-1

比较简单的题目，用来练习JAVA，代码写得有点，呵呵................

 

import java.util.*;public class Main{     static long max(long x , long y){      return x > y ? x : y;  }    static long solve(long a ,long b ,long c){      long res = 0;      while( (a >= c || b >= c) == false){          long sum = a + b;          long Max = max(a , b);          a = sum; b = Max;          res++;      }      return res;  }  static long __solve(long a , long b , long c){      long res = (-b + a - 1) / a;      long tmp = b + res * a;      res += solve(a,tmp,c);      return res;  }    public static void main(String[] args){      Scanner cin = new Scanner(System.in);      long a,b,c,res;      a = cin.nextLong();      b = cin.nextLong();      c = cin.nextLong();      if(a >= c || b >= c)          res = 0;      else if(a <= 0 && b <= 0)          res = -1;      else if(a >= 0 && b >= 0){          res = solve(a,b,c);      }      else{          long tmp;          if(a < b){              tmp = a; a = b; b = tmp;          }          res = __solve(a,b,c);      }            System.out.println(res);  }}