#include<fstream>
using namespace std;
ifstream fi("stergeri.in");
ofstream fo("stergeri.out");

int n,m,k;

void calcul(int m){
     int x,y;
     if(m){
           fi>>x>>y; 
           calcul(m-1);
           if(x<=k) k+=(y-x+1); 
          }
}

int main(){
    fi>>n>>m>>k;
     
    calcul(m); 
    fo<<k;
    
    fi.close();
    fo.close();
    return 0;
}