Problem: A smile house is created to raise the mood. It has n rooms. Some of the rooms are connected by doors. For each two rooms (number i and j), which are connected by a door, Petya knows their value cij — the value which is being added to his mood when he moves from room i to room j.

Petya wondered whether he can raise his mood infinitely, moving along some cycle? And if he can, then what minimum number of rooms he will need to visit during one period of a cycle?

Input

The first line contains two positive integers n and m (<image>), where n is the number of rooms, and m is the number of doors in the Smile House. Then follows the description of the doors: m lines each containing four integers i, j, cij и cji (1 ≤ i, j ≤ n, i ≠ j, - 104 ≤ cij, cji ≤ 104). It is guaranteed that no more than one door connects any two rooms. No door connects the room with itself.

Output

Print the minimum number of rooms that one needs to visit during one traverse of the cycle that can raise mood infinitely. If such cycle does not exist, print number 0.

Examples

Input

4 4
1 2 -10 3
1 3 1 -10
2 4 -10 -1
3 4 0 -3


Output

4

Note

Cycle is such a sequence of rooms a1, a2, ..., ak, that a1 is connected with a2, a2 is connected with a3, ..., ak - 1 is connected with ak, ak is connected with a1. Some elements of the sequence can coincide, that is, the cycle should not necessarily be simple. The number of rooms in the cycle is considered as k, the sequence's length. Note that the minimum possible length equals two.

Solution (in JAVA):

Solution:
//package que_a;

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

public class utkarsh {

    InputStream is;
    PrintWriter out;
    
    long maxl = (long) 4e18, mod = (long)1e9 + 7L;
    int maxi = (int) 2e9, P[], S[], SZ, NP = 15485900;
    boolean isP[];
    
    long[][] play(long a[][], long b[][], int n) {
        if(b == null)   return a;
        long c[][] = new long[n][n];
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                c[i][j] = a[i][j];
                for(int k = 0; k < n; k++)  c[i][j] = Math.max(c[i][j], a[i][k] + b[k][j]);
            }
        }
        return c;
    }
    
    boolean game(long[][] a, int n) {
        for(int i = 0; i < n; i++)  if(a[i][i] > 0) return true;
        return false;
    }
    
    void solve() {
        //SZ = sieve(); //SZ = 1000001;
        int n = ni(), m = ni();
        long a[][] = new long[n][n];
        for(int i = 0; i < n; i++)  Arrays.fill(a[i], -maxl);
        for(int i = 0; i < m; i++) {
            int u = ni()-1, v = ni()-1;
            a[u][v] = nl(); a[v][u] = nl();
        }
        long d[][][] = new long[9][n][n];
        d[0] = a;
        for(int i = 1; i < 9; i++)  d[i] = play(d[i-1], d[i-1], n);
        int ans = 0, cnt = 0;
        long[][] x = null, y;
        for(int i = 8; i >= 0; i--) {
            y = play(d[i], x, n);
            if(game(y, n)) {
                ans = cnt + (1 << i);
            } else {
                cnt += (1 << i);
                x = y;
            }
        }
        out.println(ans);
    }

    boolean isPrime(long n) {
        if(n <= 1)  return false;
        if(n <= 3)   return true;
        if(n%2 == 0 || n%3 == 0)    return false;
        for(long i = 5; i * i <= n; i += 6) {
            if(n % i == 0 || n % (i + 2) == 0)  return false;
        }
        return true;
    }
    
    int sieve() {
        int i, j, n = NP; 
        isP = new boolean[n]; 
        S = new int[n];
        for(i = 3; i < n; i += 2) {
            isP[i] = true;
            S[i-1] = 2;
            S[i] = i;
        }
        isP[2] = true;
        S[1] = 1;   //(UD)
        for(i = 3; i * i <= n; i += 2) {
            if( !isP[i] )   continue;
            for(j = i * i; j < n; j += i) {
                isP[j] = false;
                if(S[j] == j)   S[j] = i;
            }
        }

        P = new int[n];
        P[0] = 2;
        j = 1;
        for(i = 3; i < n; i += 2) {
            if ( isP[i] )   P[j++] = i;
        }
        P = Arrays.copyOf(P, j);
        return j;
    }

    long mp(long b, long e, long mod) {
        b %= mod;
        long r = 1;
        while(e > 0) {
            if((e & 1) == 1) {
                r *= b; r %= mod;
            }
            b *= b; b %= mod;
            e >>= 1;
        }
        return r;
    }

    //---------- I/O Template ----------
    
    public static void main(String[] args) { new utkarsh().run(); }
    void run() { 
        is = System.in; 
        out = new PrintWriter(System.out);
        solve();
        out.flush();
    }
    
    byte input[] = new byte[1024];
    int len = 0, ptr = 0;
    
    int readByte() { 
        if(ptr >= len) { ptr = 0; 
            try { len = is.read(input); } 
            catch(IOException e) { throw new InputMismatchException(); } 
            if(len <= 0) { return -1; } 
        } return input[ptr++];
    }
    boolean isSpaceChar(int c) { return !( c >= 33 && c <= 126 ); }
    int skip() { 
        int b = readByte(); 
        while(b != -1 && isSpaceChar(b)) { b = readByte(); } 
        return b;
    }
    
    char nc() { return (char)skip(); }
    String ns() { 
        int b = skip(); 
        StringBuilder sb = new StringBuilder(); 
        while(!isSpaceChar(b)) { sb.appendCodePoint(b); b = readByte(); } 
        return sb.toString();
    }
    String nLine() { 
        int b = skip(); 
        StringBuilder sb = new StringBuilder(); 
        while( !(isSpaceChar(b) && b != ' ') ) { sb.appendCodePoint(b); b = readByte(); } 
        return sb.toString();
    }
    int ni() { 
        int n = 0, b = readByte(); 
        boolean minus = false; 
        while(b != -1 && !( (b >= '0' && b <= '9') || b == '-')) { b = readByte(); } 
        if(b == '-') { minus = true; b = readByte(); } 
        if(b == -1) { return -1; }  //no input 
        while(b >= '0' && b <= '9') { n = n * 10 + (b - '0'); b = readByte(); } 
        return minus ? -n : n;
    }
    long nl() { 
        long n = 0L;    int b = readByte(); 
        boolean minus = false; 
        while(b != -1 && !( (b >= '0' && b <= '9') || b == '-')) { b = readByte(); } 
        if(b == '-') { minus = true; b = readByte(); } 
        while(b >= '0' && b <= '9') { n = n * 10 + (b - '0'); b = readByte(); } 
        return minus ? -n : n;
    }

    double nd() { return Double.parseDouble(ns()); }
    float nf() { return Float.parseFloat(ns()); }
    int[] na(int n) { 
        int a[] = new int[n]; 
        for(int i = 0; i < n; i++) { a[i] = ni(); } 
        return a;
    }
    char[] ns(int n) { 
        char c[] = new char[n]; 
        int i, b = skip(); 
        for(i = 0; i < n; i++) { 
            if(isSpaceChar(b)) { break; } 
            c[i] = (char)b; b = readByte(); 
        } return i == n ? c : Arrays.copyOf(c,i);
    }
}