#include <bits/stdc++.h>   using namespace std;   int main() {     long long a, b, c, d = 0, e = 0, f = 0, g = 0, i, j, k = 1, l = 1, r = 1,                        n[300001], m[300001], q, u, v, w, y, z[400001], h[400001],                        p[500001];     string s, t, x;     cin >> a >> b >> c;     for (i = 1; i <= a; i++) {       cin >> d >> e;       f += (d - g) / c;       g = d + e;     }     cout << f + ((b - g) / c);   }   