# include <iostream>
# include <fstream>

using namespace std;

void sol( int m, int &k, ifstream &fin ) {
    int a, b;
    fin >> a >> b;

    if ( m > 1 )
        sol( m - 1, k, fin );

    if ( a <= k )
        k += b - a + 1;
}

int main() {
    ifstream fin( "stergeri.in" );
    ofstream fout( "stergeri.out" );

    int n, m, k;

    fin >> n >> m >> k;
    sol( m, k, fin );

    fout << k;

    fin.close();
    fout.close();

    return 0;
}