Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

H, N = MAP()
A, B = [0]*N, [0]*N
for i in range(N):
	A[i], B[i] = MAP()


dp = [[INF]*(H+1) for _ in range(N+1)]
dp[0][0] = 0


for i in range(N):
	for j in range(H+1):
		if j < A[i]:
			dp[i+1][j] = min(dp[i][j], B[i])
		else:
			dp[i+1][j] = min(dp[i][j], dp[i+1][j-A[i]]+B[i])

#for i in range(0, N+1):
#	print(dp[i])

print(dp[N][H])

Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

def main():
	H, N = MAP()
	A, B = [0]*N, [0]*N
	for i in range(N):
		A[i], B[i] = MAP()

	dp = [[INF]*(H+1) for _ in range(N+1)]
	dp[0][0] = 0


	for i in range(N):
		for j in range(H+1):
			if j < A[i]:
				dp[i+1][j] = min(dp[i][j], B[i])
			if j>= A[i]:
				dp[i+1][j] = min(dp[i][j], dp[i+1][j-A[i]]+B[i])
			

	#for i in range(N+1):
	#	print(dp[i])

	print(dp[N][H])

if __name__ == '__main__':
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

def main():
	H, N = MAP()
	A, B = [0]*N, [0]*N
	for i in range(N):
		A[i], B[i] = MAP()

	dp = [[INF]*(H+1) for _ in range(N+1)]
	dp[0][0] = 0


	for i in range(N):
		for j in range(H+1):
			if j < A[i]:
				dp[i+1][j] = min(dp[i][j], B[i])
			if j>= A[i]:
				dp[i+1][j] = min(dp[i][j], dp[i][j-A[i]]+B[i], min([dp[i+1][j-A[i]*x] + B[i]*x for x in range(1, j//A[i] + 1)]))
			

	#for i in range(N+1):
	#	print(dp[i])

	print(dp[N][H])

if __name__ == '__main__':
	main()





Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

def main():
	H, N = MAP()
	A, B = [0]*N, [0]*N
	for i in range(N):
		A[i], B[i] = MAP()

	dp = [[INF]*(H+1) for _ in range(N+1)]
	dp[0][0] = 0


	for i in range(N):
		for j in range(H+1):
			if j < A[i]:
				dp[i+1][j] = min(dp[i][j], B[i])
			if j>= A[i]:
				dp[i+1][j] = min(dp[i][j], dp[i+1][j-A[i]]+B[i])
			

	#for i in range(N+1):
	#	print(dp[i])

	print(dp[N][H])

if __name__ == '__main__':
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

H, N = MAP()
A, B = [0]*N, [0]*N
for i in range(N):
	A[i], B[i] = MAP()

dp = [[INF]*(H+1) for _ in range(N+1)]
dp[0][0] = 0


for i in range(N):
	for j in range(H+1):
		if j < A[i]:
			dp[i+1][j] = min(dp[i][j], B[i])
		if j>= A[i]:
			dp[i+1][j] = min(dp[i][j], dp[i][j-A[i]]+B[i], min([dp[i+1][j-A[i]*x] + B[i]*x for x in range(1, j//A[i] + 1)]))
			

#for i in range(N+1):
#	print(dp[i])

print(dp[N][H])



Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7

def main():
	H, N = MAP()
	A, B = [0]*N, [0]*N
	for i in range(N):
		A[i], B[i] = MAP()

	dp = [[INF]*(H+1) for _ in range(N+1)]
	dp[0][0] = 0


	for i in range(N):
		for j in range(H+1):
			if j < A[i]:
				dp[i+1][j] = min(dp[i][j], B[i])
			if j>= A[i]:
				dp[i+1][j] = min(dp[i][j], dp[i+1][j-A[i]]+B[i])
			

	#for i in range(N+1):
	#	print(dp[i])

	print(dp[N][H])

if __name__ == '__main__':
	main()