from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N = int(input())
M = int(input())
A = [list(map(int,input().split())) for _ in range(M)]


##fの単位元を要考慮、matrix_powのCの初期化

def f(x,y):
    return max(x,y)
def g(x,y):
    return x+y
def matrix_mul(A,B,f,g,mod = None):
    nA = len(A)
    mA = len(A[0])
    mB = len(B[0])
    
    tmp = [[0]*mB for _ in range(nA)]
    
    if mod is None:
        for i in range(nA):
            for j in range(mB):
                tmp[i][j] = reduce(f,(g(A[i][k],B[k][j]) for k in range(mA)))
                
        return tmp
    
    for i in range(nA):
        for j in range(mB):
            tmp[i][j] = reduce(f,(g(A[i][k],B[k][j])%mod for k in range(mA)))%mod
    return tmp
    

def matrix_pow(A,n,f,g,mod = None):
    nbit = list(str(bin(n))[2:])
    nbit = [int(i) for i in nbit]
    N = len(A)
    INF = (1<<60)
    C = [[-INF]*N for _ in range(N)]
    B = A
    for i in range(N):
        C[i][i] = 0
        
    if mod is None:
        if f is None:
            for i in range(len(nbit)):
                if nbit[-1-i] == 1:
                    C = matrix_mul(C,B,f,g)
                
                B = matrix_mul(B,B,f,g)
            return C
        
    for i in range(len(nbit)):
        if nbit[-1-i] == 1:
            C = matrix_mul(C,B,f,g,mod=mod)
        
        B = matrix_mul(B,B,f,g,mod=mod)
    
    return C 
    
I = [[0] for _ in range(M)]
X = matrix_mul(matrix_pow(A,N-1,f,g),I,f,g)
ans = -1
for x in X:
    ans = max(ans,x[0])
print(ans)