#include <iostream.h>
#include <fstream.h>

fstream f1,f2;
long N,M,K,k;

void Init(void)
{
 N = 0;
 M = 0;
 K = 0;
}

void Citeste(void)
{
 f1 >> N >> M >> K;
 k = K;
}

long Afla(long m)
{
 if (m == 0)
   {
    return k;
   }
 long nmin,nmax;
 f1 >> nmin >> nmax;
 k = Afla(m - 1);
 if (nmin <= k)
   {
    k += nmax - nmin + 1;
   }
 return k;
}

int main(void)
{
 f1.open("stergeri.in",ios::in);
 f2.open("stergeri.out",ios::out);
 Citeste();
 f2 << Afla(M);
 f1.close();
 f2.close();
 return 0;
}