#include <stdio.h>

int max=0;
int n,m,k,rsp,q=0; //!!!!!  ATENTIE lA 0 !! VAAACOOO !! (Made by `GhOsT`)(CS name)
unsigned char a[20002];

int BS(int st,int dr,int V)
{
	int m;
	if (st>dr) return -1; else
	{
		m=(st+dr)/2;
		if (V==a[m]) return m;
		else if (V<a[m]) return BS(st,m-1,V); else return BS(m+1,dr,V);
	}
}

void fatotul(int x,int y)
{
	if (q!=0)
	{
		int rasp1;
		rasp1=BS(1,q*2,x);
		if (rasp1!=-1)
		{
			fatotul(a[rasp1+1]+1,a[rasp1+1]+1+y-x);
		} else {a[2*(++q)]=y;a[2*q-1]=x;}
	} else {a[2*(++q)]=y;a[2*q-1]=x;}

}
void citeste()
{
	scanf("%d %d %d",&n,&m,&k);
	int x=0,y=0,i=0;
	for (i=1;i<=m;i++)
	{
		scanf("%d %d",&x,&y);
		fatotul(x,y);
	}
	for (i=1;i<=q*2;i++) if (max<a[i]) max=a[i];
	rsp=max+k;
}

int main()
{
	freopen("stergeri.in","r",stdin);
	freopen("stergeri.out","w",stdout);
	citeste();
	printf("%d",rsp);

	return 0;
}