#include<stdio.h>
#define DIM 100001
int i,n,m,k,x[DIM],y[DIM],k1;
int main ()
{
    freopen("stergeri.in","r",stdin);
    freopen("stergeri.out","w",stdout);
    scanf("%d%d%d",&n,&m,&k);
    for(i=1;i<=m;++i)
    scanf("%d%d",&x[i],&y[i]);
    for(i=m;i>0;--i)
    {
     k1=y[i]-x[i]+1;
     k+=k1;
    }
    printf("%d",k);
    return 0;
}