Buggy python submission (verdict: Time Limit Exceeded):
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = [0]*(m-1)
    x.sort()
    for i in range(m-1):
        sa[i] = x[i+1] - x[i]
    for i in range(spl):
        sa.remove(max(sa))
    print(sum(sa))



main()


Fixed submission:
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = [0]*(m-1)
    x.sort()
    for i in range(m-1):
        sa[i] = x[i+1] - x[i]
    sa.sort()
    i = m-n
    print(sum(sa[:i]))



main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = [0]*(m-1)
    x.sort()
    for i in range(m-1):
        sa[i] = x[i+1] - x[i]
    for i in range(spl):
        sa.pop(sa.index(max(sa)))
    print(sum(sa))



main()


Fixed submission:
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = [0]*(m-1)
    x.sort()
    for i in range(m-1):
        sa[i] = x[i+1] - x[i]
    sa.sort()
    i = m-n
    print(sum(sa[:i]))



main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = []
    x.sort()
    for i in range(m-1):
        sa.append(x[i+1] - x[i])
    for i in range(spl):
        sa.pop(sa.index(max(sa)))
    print(sum(sa))



main()


Fixed submission:
import sys
#from collections import defaultdict, deque, Counter
#import bisect
#import heapq
#import math
#from itertools import accumulate
#from itertools import permutations as perm
#from itertools import combinations as comb
#from itertools import combinations_with_replacement as combr
#from fractions import gcd
#import numpy as np

stdin = sys.stdin
sys.setrecursionlimit(10 ** 7)
MIN = -10 ** 9
MOD = 10 ** 9 + 7
INF = float("inf")
IINF = 10 ** 18

def main():
    #n = int(stdin.readline().rstrip())
    n,m = map(int, stdin.readline().rstrip().split())
    x = list(map(int, stdin.readline().rstrip().split()))
    #numbers = [[int(c) for c in l.strip().split()] for l in sys.stdin]
    #word = [stdin.readline().rstrip() for _ in range(n)]
    #number = [[int(c) for c in stdin.readline().rstrip()] for _ in range(n)]
    #zeros = [[0] * w for i in range(h)]
    if n>m:
        print(0)
        exit()
    spl = n-1
    sa = [0]*(m-1)
    x.sort()
    for i in range(m-1):
        sa[i] = x[i+1] - x[i]
    sa.sort()
    i = m-n
    print(sum(sa[:i]))



main()