Buggy python submission (verdict: Time Limit Exceeded):
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    sum[i] = sum[i-1] + cnt[i]

print(cnt[-1] % mod)

Fixed submission:
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    cnt[i] %= mod
    sum[i] = (sum[i-1] + cnt[i]) % mod

print(cnt[-1])

Buggy python submission (verdict: Time Limit Exceeded):
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if s[j][0] == s[j][1] and i >= s[j][0]:
      cnt[i] += cnt[i-s[j][0]]
    elif i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    sum[i] = sum[i-1] + cnt[i]

print(cnt[-1] % mod)

Fixed submission:
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    cnt[i] %= mod
    sum[i] = (sum[i-1] + cnt[i]) % mod

print(cnt[-1])

Buggy python submission (verdict: Time Limit Exceeded):
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if s[j][0] == s[j][1] and i >= s[j][0]:
      cnt[i] += cnt[i-s[j][0]]
    elif i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    sum[i] = sum[i-1] + cnt[i]

print(cnt[-1] % mod)

Fixed submission:
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    cnt[i] %= mod
    sum[i] = (sum[i-1] + cnt[i]) % mod

print(cnt[-1])

Buggy python submission (verdict: Time Limit Exceeded):
n, k = map(int,input().split())
s = []
mod = 998244353
for i in range(k):
  l, r = map(int,input().split())
  for j in range(l,r+1):
    s.append(j)
s.sort()
cnt = [0]*n
cnt[0] = 1
for i in range(n):
  for d in range(len(s)):
    if i+s[d] <= n-1:
      cnt[i+s[d]] += cnt[i]
    elif i+s[d] > n-1:
      break
print(cnt[-1] % mod)

Fixed submission:
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    cnt[i] %= mod
    sum[i] = (sum[i-1] + cnt[i]) % mod

print(cnt[-1])

Buggy python submission (verdict: Time Limit Exceeded):
n, k = map(int,input().split())
s = []
mod = 998244353
for i in range(k):
  l, r = map(int,input().split())
  for j in range(l,r+1):
    s.append(j)
s.sort()
cnt = [0]*n
cnt[0] = 1
for i in range(n):
  for d in range(len(s)):
    if i+s[d] <= n-1:
      cnt[i+s[d]] += cnt[i]
    elif i+s[d] > n-1:
      break
print(cnt[-1] % mod)

Fixed submission:
#dpで素直にやるとO(N^2)だから、累積和で高速化しO(KN)にする

n, k = map(int,input().split())
mod = 998244353

s = []
for i in range(k):
  s.append(list(map(int,input().split())))

cnt = [0]*n
cnt[0] = 1
sum = [0]*n
sum[0] = 1
for i in range(1,n):
  for j in range(k):
    if i > s[j][1]:
      cnt[i] += sum[i-s[j][0]] - sum[i-s[j][1]-1]
    elif i >= s[j][0]:
      cnt[i] += sum[i-s[j][0]]
    cnt[i] %= mod
    sum[i] = (sum[i-1] + cnt[i]) % mod

print(cnt[-1])