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