#include <fstream>
using namespace std;
ifstream fin("stergeri.in");
ofstream fout("stergeri.out");
int n,m,k,a,b,i;
int main(){
    fin>>n>>m>>k;
    for(i=1;i<=m;i++){
        fin>>a>>b;
        k=k+b-a+1;
    }
    fout<<k<<"\n";




    return 0;
}