import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.NoSuchElementException; public class Main implements Runnable { public static void main(String[] args) { new Main().run(); } public void run() { solve(); } long[][] mul(long[][] a, long[][] b) { if (a==null) return b; if (b==null) return a; long[][] c=new long[a.length][b[0].length]; for (int i=0;iY) { X^=Y;Y^=X;X^=Y; } if (X!=1) { X=X+1; } if (Y!=N) { Y=Y-1; } if (X>Y) { System.out.println(0); return; } N=Y-X+1; long[][] a=new long[][] {{1, 0, 1}, {1, 0, 0}, {0, 1, 0}}; long[][] v=new long[][] {{1},{1},{1}}; a=pow(a, N-1); a=mul(a, v); System.out.println(a[2][0]); pw.close(); } static void tr(Object...objects) { System.out.println(Arrays.deepToString(objects)); } } class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; }else{ ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;} private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;} private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;} public boolean hasNext() { skipUnprintable(); return hasNextByte();} public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while(isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while(true){ if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; }else if(b == -1 || !isPrintableChar(b)){ return minus ? -n : n; }else{ throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { return (int)nextLong(); } }