func_code_string: #include <bits/stdc++.h>   using namespace std;   long long a[200010];   long long l[200010];   long long r[200010];   int main() {     ios_base::sync_with_stdio(0);     long long n, h;     cin >> n >> h;     vector<long long> rast2(n + 1, 0);     for (int i = 1; i <= n; i++) {       cin >> l[i] >> r[i];       rast2[i] = r[i] - l[i];     }     for (int i = 1; i <= n; i++) {       rast2[i] += rast2[i - 1];     }     vector<long long> rast(n + 1, 0);     for (int i = 1; i < n; i++) {       rast[i] = l[i + 1] - r[i];     }     rast[n] = 2e9;     for (int i = 1; i <= n; i++) {       rast[i] += rast[i - 1];     }     long long ans = 0;     for (int i = 1; i <= n; i++) {       long long r =           lower_bound(rast.begin(), rast.end(), h + rast[i - 1]) - (rast.begin());       if (r <= n) ans = max(ans, (rast2[r] - rast2[i - 1]) + h);     }     cout << ans;   }   