#include<fstream>
using namespace std;

int main(void){
    ifstream fin("stergeri.in");
    ofstream fout("stergeri.out");
    int n,m,k,x,y,buf=0,nr;
    fin>>n>>m>>k; nr=k;
    while(m--){
               fin>>x>>y;
               if(x>k)buf+=y-x+1;
                else
                {
                  nr+=buf+y-x+1;
                  buf=0;
                  }                
               }
    fout<<nr;
 return 0;   
}