import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines

class Graph:
    def __init__(self,V,edges=False,graph=False,directed=False,weighted=False,inf=float("inf")):
        self.V=V
        self.directed=directed
        self.weighted=weighted
        self.inf=inf
        if graph:
            self.graph=graph
            self.edges=[]
            for i in range(self.V):
                if self.weighted:
                    for j,d in self.graph[i]:
                        if self.directed or not self.directed and i<=j:
                            self.edges.append((i,j,d))
                else:
                    for j in self.graph[i]:
                        if self.directed or not self.directed and i<=j:
                            self.edges.append((i,j))
        else:
            self.edges=edges
            self.graph=[[] for i in range(self.V)]
            if weighted:
                for i,j,d in self.edges:
                    self.graph[i].append((j,d))
                    if not self.directed:
                        self.graph[j].append((i,d))
            else:
                for i,j in self.edges:
                    self.graph[i].append(j)
                    if not self.directed:
                        self.graph[j].append(i)

    def SIV_BFS(self,s,bfs_tour=False,bipartite_graph=False,linked_components=False,parents=False,unweighted_dist=False,weighted_dist=False):
        seen=[False]*self.V
        seen[s]=True
        if bfs_tour:
            bt=[s]
        if linked_components:
            lc=[s]
        if parents:
            ps=[None]*self.V
        if unweighted_dist or bipartite_graph:
            uwd=[self.inf]*self.V
            uwd[s]=0
        if weighted_dist:
            wd=[self.inf]*self.V
            wd[s]=0
        queue=deque([s])
        while queue:
            x=queue.popleft()
            for y in self.graph[x]:
                if self.weighted:
                    y,d=y
                if not seen[y]:
                    seen[y]=True
                    queue.append(y)
                    if bfs_tour:
                        bt.append(y)
                    if linked_components:
                        lc.append(y)
                    if parents:
                        ps[y]=x
                    if unweighted_dist or bipartite_graph:
                        uwd[y]=uwd[x]+1
                    if weighted_dist:
                        wd[y]=wd[x]+d
        if bipartite_graph:
            bg=[[],[]]
            for tpl in self.edges:
                i,j=tpl[:2] if self.weighted else tpl
                if uwd[i]==self.inf or uwd[j]==self.inf:
                    continue
                if not uwd[i]%2^uwd[j]%2:
                    bg=False
                    break
            else:
                for x in range(self.V):
                    if uwd[x]==self.inf:
                        continue
                    bg[uwd[x]%2].append(x)
        retu=()
        if bfs_tour:
            retu+=(bt,)
        if bipartite_graph:
            retu+=(bg,)
        if linked_components:
            retu+=(lc,)
        if parents:
            retu+=(ps,)
        if unweighted_dist:
            retu+=(uwd,)
        if weighted_dist:
            retu+=(wd,)
        if len(retu)==1:
            retu=retu[0]
        return retu
class Cumsum:
    def __init__(self,lst,mod=0):
        self.N=len(lst)
        self.mod=mod
        self.cumsum=[0]*(self.N+1)
        self.cumsum[0]=0
        for i in range(1,self.N+1):
            self.cumsum[i]=self.cumsum[i-1]+lst[i-1]
            if self.mod:
                self.cumsum[i]%=self.mod

    def __getitem__(self,i):
        if type(i)==int:
            if 0<=i<self.N:
                a,b=i,i+1
            elif -self.N<=i<0:
                a,b=i+self.N,i+self.N+1
            else:
                raise IndexError('list index out of range')
        else:
            a,b=i.start,i.stop
            if a==None or a<-self.N:
                a=0
            elif self.N<=a:
                a=self.N
            elif a<0:
                a+=self.N
            if b==None or self.N<=b:
                b=self.N
            elif b<-self.N:
                b=0
            elif b<0:
                b+=self.N
        s=self.cumsum[b]-self.cumsum[a]
        if self.mod:
            s%=self.mod
        return s

    def __setitem__(self,i,x):
        if -self.N<=i<0:
            i+=self.N
        elif not 0<=i<self.N:
            raise IndexError('list index out of range')
        self.cumsum[i+1]=self.cumsum[i]+x
        if self.mod:
            self.cumsum[i+1]%=self.mod

    def __str__(self):
        lst=[self.cumsum[i+1]-self.cumsum[i] for i in range(self.N)]
        if self.mod:
            for i in range(self.N):
                lst[i]%=self.mod
        return "["+", ".join(map(str,lst))+"]"

N,K,P=map(int,readline().split())
points=[(i,j) for i in range(N) for j in range(i+1)]
idx={points[i]:i+1 for i in range(len(points))}
edges=[]
for i in range(N):
    for j in range(i):
        edges.append((idx[(i,j)],idx[(i,j+1)]))
        edges.append((idx[(i,j+1)],idx[(i,j)]))
for i in range(N-1):
    for j in range(i+1):
        edges.append((idx[(i,j)],idx[(i+1,j)]))
        edges.append((idx[(i,j)],idx[(i+1,j+1)]))
        edges.append((idx[(i+1,j)],idx[(i,j)]))
        edges.append((idx[(i+1,j+1)],idx[(i,j)]))
for _ in range(K):
    x,y=map(int,readline().split())
    x-=1;y-=1
    edges.append((0,idx[(x,y)]))
G=Graph(len(points)+1,edges=edges,directed=True)
dist=G.SIV_BFS(0,unweighted_dist=True)
A=[[None]*(i+1) for i in range(N)]
for i,(x,y) in enumerate(points,1):
    A[x][y]=dist[i]-1
AL=[[A[i][j] for j in range(i+1)] for i in range(N)]
AR=[[A[i][j] for j in range(i+1)] for i in range(N)]
for i in range(1,N):
    for j in range(i):
        AL[i][j]+=AL[i-1][j]
for i in range(1,N):
    for j in range(1,i+1):
        AR[i][j]+=AR[i-1][j-1]
for i in range(N):
    A[i]=Cumsum(A[i])
ans=0
dp=[[(0,0)]*(i+1) for i in range(N)]
for i in range(N):
    for j in range(i+1):
        ii,s=dp[i][j]
        while ii<N and s<P:
            s+=A[ii][j:j-i+ii+1]
            ii+=1
        dp[i][j]=(ii,s)
        if i!=N-1:
            dp[i+1][j]=max(dp[i+1][j],(ii,s-(AR[ii-1][j-i+ii-1]-(AR[i-1][j-1] if i and j else 0))))
            dp[i+1][j+1]=max(dp[i+1][j+1],(ii,s-(AL[ii-1][j]-(AL[i-1][j] if i and i!=j else 0))))
ans=0
for i in range(N):
    for j in range(i+1):
        if dp[i][j][1]>=P:
            ans+=N-dp[i][j][0]+1
print(ans)