#include <stdio.h>
#include <stdlib.h>
struct{ int x, y ;} v[100001];
int main()
{
    freopen("stergeri.in", "r", stdin);
    freopen("stergeri.out", "w", stdout);
    int n, m, k, i;
    scanf("%d%d%d", &n, &m, &k);
    for(i = 1; i <= n; i++ )
        scanf("%d%d", &v[i].x, &v[i].y);
    int nr = k;
    for (i = m; i >=1 ; i--)
        nr += v[i].y - v[i].x +1;
    printf("%d", nr);
    return 0;
}