Polycarp lives on a coordinate line at the point $x = 0$. He goes to his friend that lives at the point $x = a$. Polycarp can move only from left to right, he can pass one unit of length each second.

Now it's raining, so some segments of his way are in the rain. Formally, it's raining on $n$ non-intersecting segments, the $i$-th segment which is in the rain is represented as $[l_i, r_i]$ ($0 \le l_i < r_i \le a$).

There are $m$ umbrellas lying on the line, the $i$-th umbrella is located at point $x_i$ ($0 \le x_i \le a$) and has weight $p_i$. When Polycarp begins his journey, he doesn't have any umbrellas.

During his journey from $x = 0$ to $x = a$ Polycarp can pick up and throw away umbrellas. Polycarp picks up and throws down any umbrella instantly. He can carry any number of umbrellas at any moment of time. Because Polycarp doesn't want to get wet, he must carry at least one umbrella while he moves from $x$ to $x + 1$ if a segment $[x, x + 1]$ is in the rain (i.e. if there exists some $i$ such that $l_i \le x$ and $x + 1 \le r_i$).

The condition above is the only requirement. For example, it is possible to go without any umbrellas to a point where some rain segment starts, pick up an umbrella at this point and move along with an umbrella. Polycarp can swap umbrellas while he is in the rain.

Each unit of length passed increases Polycarp's fatigue by the sum of the weights of umbrellas he carries while moving.

Can Polycarp make his way from point $x = 0$ to point $x = a$? If yes, find the minimum total fatigue after reaching $x = a$, if Polycarp picks up and throws away umbrellas optimally.


-----Input-----

The first line contains three integers $a$, $n$ and $m$ ($1 \le a, m \le 2000, 1 \le n \le \lceil\frac{a}{2}\rceil$) — the point at which Polycarp's friend lives, the number of the segments in the rain and the number of umbrellas.

Each of the next $n$ lines contains two integers $l_i$ and $r_i$ ($0 \le l_i < r_i \le a$) — the borders of the $i$-th segment under rain. It is guaranteed that there is no pair of intersecting segments. In other words, for each pair of segments $i$ and $j$ either $r_i < l_j$ or $r_j < l_i$.

Each of the next $m$ lines contains two integers $x_i$ and $p_i$ ($0 \le x_i \le a$, $1 \le p_i \le 10^5$) — the location and the weight of the $i$-th umbrella.


-----Output-----

Print "-1" (without quotes) if Polycarp can't make his way from point $x = 0$ to point $x = a$. Otherwise print one integer — the minimum total fatigue after reaching $x = a$, if Polycarp picks up and throws away umbrellas optimally.


-----Examples-----
Input
10 2 4
3 7
8 10
0 10
3 4
8 1
1 2

Output
14

Input
10 1 1
0 9
0 5

Output
45

Input
10 1 1
0 9
1 5

Output
-1



-----Note-----

In the first example the only possible strategy is to take the fourth umbrella at the point $x = 1$, keep it till the point $x = 7$ (the total fatigue at $x = 7$ will be equal to $12$), throw it away, move on from $x = 7$ to $x = 8$ without an umbrella, take the third umbrella at $x = 8$ and keep it till the end (the total fatigue at $x = 10$ will be equal to $14$). 

In the second example the only possible strategy is to take the first umbrella, move with it till the point $x = 9$, throw it away and proceed without an umbrella till the end.

Difficulty: introductory

Starter code:

Solutions:
import sys
a,m,n=list(map(int,input().split()))
aux=[0]*(a+1)
inf=10**15
dp=[aux.copy() for i in range(n+1)]
m1=10**12
m2=10**12
for i in range(m):
    l,r=list(map(int,input().split()))
    if l<m1:
        m1=l
    for j in range(l,r):
        dp[0][j+1]=inf
s=[]
for i in range(1,n+1):
    x,w=list(map(int,input().split()))
    s.append(tuple([x,w]))
    if x<m2:
        m2=x
if m2>m1:
    print(-1)
    return
s.sort()

for i in range(1,n+1):
    x=s[i-1][0]
    w=s[i-1][1]
    for j in range(x+1):
        dp[i][j]=dp[i-1][j]
    for j in range(x+1,a+1):
        if i!=1:
            dp[i][j]=min(dp[0][j]+dp[i][j-1],dp[i-1][j],w*(j-x)+dp[i][x])
        else:
            dp[i][j]=min(dp[0][j]+dp[i][j-1],w*(j-x)+dp[i][x])
            
ans=dp[-1][-1]
if ans>=inf:
    print(-1)
else:
    print(ans)


import sys
a, n, m = list(map(int, input().split(' ')))

seg = []
for i in range(n):
    rained = tuple(map(int, input().split(' ')))
    for k in range(rained[0], rained[1]):
        seg.append(k+1)

umbrella = []
for j in range(m):
    u = tuple(map(int, input().split(' ')))
    umbrella.append(u)

memo = [0] * (a+1)

umbrella = sorted(umbrella, key=lambda x: x[0])
if umbrella[0][0] > seg[0] - 1:
    print(-1)
    return

for index in range(1, len(memo)):

    if index not in seg:
        memo[index] = memo[index-1]
        continue

    for each in umbrella:
        if index >= each[0]:
            cur = (index - each[0]) * each[1] + memo[each[0]]
            if memo[index] > 0:
                if cur < memo[index]:
                    memo[index] = cur
            else:
                memo[index] = cur






print(memo[-1])












#     Codeforces Round #486 (Div. 3)

from functools import cmp_to_key
#key=cmp_to_key(lambda x,y: 1 if x not in y else -1 )

import sys
def getIntList():
    return list(map(int, input().split()))    



a,n,m = getIntList()
rainend = set()
umbr = {}
keyPointSet = set([0,a])
for i in range(n):
    t =tuple(getIntList()) 
    for j in range(t[0] + 1, t[1] + 1):
        rainend.add(j)
    keyPointSet.add(t[1])
for i in range(m):
    t =getIntList()
    if t[0] not in umbr or t[1]< umbr[t[0]]:
        umbr[t[0]] = t[1]
    keyPointSet.add(t[0])
    
keyPoint = list(keyPointSet)
keyPoint.sort()



dp = {}

dp[0] =  {}
dp[0] [0] = 0
if 0 in umbr:
    dp[0][umbr[0]] = 0


for i in range(1, len(keyPoint)):
    x = keyPoint[i]
    lx = keyPoint[i-1]
    ifrain =  x in rainend
    dp[x] = {}
    nowdp = dp[x]
    lastdp = dp[lx]
    
    for z in lastdp:
        if z == 0 :
            if not ifrain:
                nowdp[0] = lastdp[0]
        else:
            nowdp[z]  = lastdp[z] + z * (x-lx)
    if len(nowdp) >0:
        nowdp[0] = min(nowdp.values())
        if x in umbr:
            if umbr[x] not in nowdp or   nowdp[0] < nowdp[umbr[x]]:
                nowdp[umbr[x]] = nowdp[0]
    else:
        print(-1)
        return

print( min(dp[a].values()) )
            
    


rd = lambda: list(map(int, input().split()))
a, n, m = rd()
s = set()
u = {}
k = set([0, a])
for _ in range(n):
    l, r = rd()
    for x in range(l + 1, r + 1):
        s.add(x)
    k.add(r)
for _ in range(m):
    x, p = rd()
    u[x] = min(p, u.get(x, 1e9))
    k.add(x)
k = sorted(list(k))
dp = {}
dp[0] = {}
dp[0][0] = 0
if 0 in u:
    dp[0][u[0]] = 0
for i in range(1, len(k)):
    x = k[i]
    y = k[i - 1]
    dp[x] = {}
    for z in dp[y]:
        if z:
            dp[x][z] = dp[y][z] + z * (x - y)
        else:
            if x not in s:
                dp[x][0] = dp[y][0]
    if len(dp[x]):
        dp[x][0] = min(dp[x].values())
        if x in u:
            if u[x] not in dp[x] or dp[x][0] < dp[x][u[x]]:
                dp[x][u[x]] = dp[x][0]
    else:
        print(-1)
        return
print(dp[a][0])


import sys

def input():
    return sys.stdin.readline().strip()

def input_l():
    return map(int, input().split())

def input_t():
    return tuple(input_l())
    
def main():
    a, s, d = input_l()
    q = []
    e = []
    z = [0] * (a + 1)
    
    for i in range(s):
        w = input_t()
        for k in range(w[0], w[1]):
            q.append(k + 1)

    for j in range(d):
        e.append(input_t())
    
    e = sorted(e, key = lambda x: x[0])
    
    if e[0][0] > q[0] - 1:
        print(-1)
        return
    
    for i in range(1, len(z)):
        if i not in q:
            z[i] = z[i-1]
            continue
    
        for j in e:
            if i >= j[0]:
                c = (i - j[0]) * j[1] + z[j[0]]
                if z[i] > 0:
                    if c < z[i]:
                        z[i] = c            
                else:
                    z[i] = c
    
    print(z[-1])
    
main()

import math


def main():
    a, n, m = list(map(int, input().split()))
    rain = []
    u = []
    w = []
    raining = [False] * (a+1)
    for i in range(n):
        l, r = list(map(int, input().split()))
        rain.append((l, r))
        for j in range(l, r):
            raining[j] = True

    for i in range(m):
        x, y = list(map(int, input().split()))
        u.append(x)
        w.append(y)

    rain_int = [0] * a
    for i in range(n):
        rain_int[rain[i][0]-1] = 1
        rain_int[rain[i][1]-1] = -1

    umbrellas = [-1 for _ in range(a+1)]
    for i, x in enumerate(u):
        if umbrellas[x] == -1 or w[umbrellas[x]] > w[i]:
            umbrellas[x] = i

    dp = [[math.inf for _ in range(m+1)] for _ in range(a+1)]
    dp[0][m] = 0
    for i in range(a):
        for j in range(m+1):
            if dp[i][j] == math.inf:
                continue
            if not raining[i]:
                dp[i+1][m] = min(dp[i+1][m], dp[i][j])
            if j < m:
                dp[i+1][j] = min(dp[i+1][j], dp[i][j] + w[j])
            if umbrellas[i] != -1:
                dp[i+1][umbrellas[i]] = min(dp[i+1][umbrellas[i]], dp[i][j]+w[umbrellas[i]])

    ans = math.inf
    for i in range(m+1):
        ans = min(ans, dp[a][i])
    print(-1 if ans == math.inf else ans)


def __starting_point():
    main()

__starting_point()

# Author: S Mahesh Raju
# Username: maheshraju2020
# Date: 03/07/2020

from sys import stdin,stdout
from math import gcd, ceil, sqrt
from collections import Counter
ii1 = lambda: int(stdin.readline().strip())
is1 = lambda: stdin.readline().strip()
iia = lambda: list(map(int, stdin.readline().strip().split()))
isa = lambda: stdin.readline().strip().split()
mod = 1000000007

a, n, m = iia()
rain = []
for _ in range(n):
    l, r = iia()
    for i in range(l, r):
        rain.append(i)
umb = []
for _ in range(m):
    umb.append(iia())

rain.sort()
umb.sort()

dp = [0] * (a + 1)
for i in range(a + 1):
    if i not in rain:
        if i != 0:
            dp[i] = dp[i - 1]
    
    else:
        for j in umb:
            if j[0] <= i:
                temp = (i + 1 - j[0]) * j[1]

                if j[0] - 1 >= 0:
                    temp += dp[j[0] - 1]

                if dp[i] > 0:
                    dp[i] = min(dp[i], temp)
                
                else:
                    dp[i] = temp
                
            else:
                break

# print(dp)

if umb[0][0] > rain[0]:
    print(-1)
else:
    print(dp[-1])



# -*- coding: utf-8 -*-
import sys
from collections import deque, defaultdict, namedtuple
from math import sqrt, factorial, gcd, ceil, atan, pi
def input(): return sys.stdin.readline()[:-1] # warning not \n
# def input(): return sys.stdin.buffer.readline().strip() # warning bytes
# def input(): return sys.stdin.buffer.readline().decode('utf-8')
import string
import operator
# string.ascii_lowercase
from bisect import bisect_left, bisect_right
from functools import lru_cache, reduce
MOD = int(1e9)+7
INF = float('inf')


def solve():
    a, n, m = [int(x) for x in input().split()]
    rain = [0] * (a + 1)
    for _ in range(n):
        l, r = [int(x) for x in input().split()]
        for i in range(l + 1, r + 1):
            rain[i] = 1
    umb = []
    for _ in range(m):
        x, p = [int(x) for x in input().split()]
        umb.append((x, p))
    umb.sort()

    dp = [INF for _ in range(a + 1)]
    dp[0] = 0
    for i in range(1, a + 1):
        if rain[i]:
            for x, p in umb:
                if x >= i: break
                dp[i] = min(dp[i], dp[x] + p * (i - x))
        else:
            dp[i] = dp[i-1]

    if dp[a] == INF:
        print(-1)
    else:
        print(dp[a])



t = 1
# t = int(input())
for case in range(1,t+1):
    ans = solve()


"""

1 2

dp[x] = min()




"""


from bisect import bisect_left as bl
from bisect import bisect_right as br
from heapq import heappush,heappop,heapify
import math
from collections import *
from functools import reduce,cmp_to_key
import sys
input = sys.stdin.readline

from itertools import accumulate
from functools import lru_cache

M = mod = 998244353
def factors(n):return sorted(set(reduce(list.__add__, ([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0))))
def inv_mod(n):return pow(n, mod - 2, mod)
 
def li():return [int(i) for i in input().rstrip('\n').split()]
def st():return input().rstrip('\n')
def val():return int(input().rstrip('\n'))
def li2():return [i for i in input().rstrip('\n')]
def li3():return [int(i) for i in input().rstrip('\n')]


sys.setrecursionlimit(10 ** 6)

a, n, m = li()
l = []
rain = defaultdict(int)
for i in range(n):
    c, b = li()
    for j in range(c, b):
        rain[(j, j + 1)] = 1


# print(rain)
umbrellas = [float('inf')] * (a + 5)
for i in range(m):
    c, b = li()
    umbrellas[c] = min(umbrellas[c], b)
# print(umbrellas[:a + 1])

@lru_cache(None)
def dp(i = 0, umbon = 0):
    # print(i, umbon)
    if i == a:
        if rain[(i - 1, i)]:
            if umbon:return umbon
            return float('inf')
        else:return umbon
    else:
        ans = float('inf')
        last = umbon
        if rain[(i - 1, i)]:
            umbon = min(umbon, umbrellas[i]) if umbon else umbrellas[i]
            if not last:last = float('inf')
            ans = min(ans, last + dp(i + 1, umbon))
            ans = min(ans, last + dp(i + 1, 0))
        else:
            ans = min(ans, dp(i + 1, 0) + last)
            umbon = min(umbon, umbrellas[i]) if umbon else umbrellas[i]
            ans = min(ans, dp(i + 1, umbon) + last)
    return ans

print(dp(0, 0) if dp(0, 0) != float('inf') else -1)