cf Perfect Pair

http://codeforces.com/contest/318/problem/C

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 using namespace std;

 5 long long j;

 6 long long x,y,m;

 7 int main()

 8 {

 9     scanf("%I64d%I64d%I64d",&x,&y,&m);

10     if(x>=m||y>=m)

11     {

12         printf("0\n");

13         return 0;

14     }

15     else if(x<=0&&y<=0)

16     {

17         printf("-1\n");

18         return 0;

19     }

20     if(x<0)

21     {

22         j=(-x)/y+1;

23         x+=j*y;

24     }

25     if(y<0)

26     {

27         j=(-y)/x+1;

28         y+=j*x;

29     }

30     while(1)

31     {

32         if(!(x<m&&y<m)) break;

33         if(x>y) y=x+y;

34         else x=x+y;

35         j++;

36     }

37     printf("%I64d\n",j);

38     return 0;

39 }

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