#include<fstream>
using namespace std;
ifstream fin("stergeri.in");
ofstream fout("stergeri.out");
int n,m,k,x,y,i;
int main(){
    fin>>n>>m>>k;
    for(i=1;i<=m;i++){
        fin>>x>>y;
            k+=y-x+1;
    }
    fout<<k;
    return 0;
}