# include <stdio.h>
long int x,y,n,m,k,i;
int main ()
{
freopen ("stergeri.in","r",stdin);
freopen ("stergeri.out","w",stdout);
scanf ("%li",&n);
scanf ("%li",&m);
scanf ("%li",&k);
for (i=0;i<m;i++)
{
scanf ("%li",&x);
scanf ("%li",&y);
k=k+(y-x+1);
}
printf ("%li",k);
return 0;
}