Let us call a pair of integer numbers m-perfect, if at least one number in the pair is greater than or equal to m. Thus, the pairs (3, 3) and (0, 2) are 2-perfect while the pair (-1, 1) is not.

Two integers x, y are written on the blackboard. It is allowed to erase one of them and replace it with the sum of the numbers, (x + y).

What is the minimum number of such operations one has to perform in order to make the given pair of integers m-perfect?

Input

Single line of the input contains three integers x, y and m ( - 1018 ≤ x, y, m ≤ 1018).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preffered to use the cin, cout streams or the %I64d specifier.

Output

Print the minimum number of operations or "-1" (without quotes), if it is impossible to transform the given pair to the m-perfect one.

Examples

Input

1 2 5


Output

2


Input

-1 4 15


Output

4


Input

0 -1 5


Output

-1

Note

In the first sample the following sequence of operations is suitable: (1, 2) <image> (3, 2) <image> (5, 2).

In the second sample: (-1, 4) <image> (3, 4) <image> (7, 4) <image> (11, 4) <image> (15, 4).

Finally, in the third sample x, y cannot be made positive, hence there is no proper sequence of operations.
//MohammedElkady
import java.io.IOException;
import java.io.InputStream;
import java.util.*;
public class Hell {
static long ans;

    public static void main(String[] args) {
        Reader in =new Reader();
        long x=in.l(),y=in.l(),m=in.l();
       long min=Math.min(x, y);
       long max=Math.max(x, y);
       if(max<=0&&min<=0){
           if(m<=max)System.out.println("0");
           else
           System.out.println(-1);return;}
       if(min<0&&m>max){
       ans=Math.abs(min)/max;
       min+=(ans*max);
       }
       while(max<m){
       ans++;
       min=max+min;
       if(min>max){x=max;max=min;min=x;}
       }
        System.out.println(ans);
}
 static class Reader 
    { 
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public Reader() { this(System.in); }public Reader(InputStream is) { mIs = is;} 
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];} 
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;} 
        public String s(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();} 
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;} 
        public int nextInt(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;} 
        public double d() throws IOException {return Double.parseDouble(s()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } 
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; } 
        public int[] arr(int n){int[] ret = new int[n];for (int i = 0; i < n; i++) {ret[i] = nextInt();}return ret;}
    }   
}
class HashTable{
List[]Table;
HashTable(int size){
Table=new List[size];
while(size-->0){
Table[size]=new ArrayList();
}
}
void Hashing(int kay,int value){
Table[kay].add(value);
}
void Delet(int key,int value){
for(int i=0;i<Table[key].size();i++)
    if(value==(int)Table[key].get(i)){
        Table[key].remove(i);i--;}
}
ArrayList getTable(int key){
    return (ArrayList) Table[key];

}
void Uptodate(int key ,int value , int nextvalue){
for(int i=0;i<Table[key].size();i++)
    if(Table[key].get(i).equals(value)){
        Table[key].remove(i);Table[key].add(nextvalue);i--;}

}
}