func_code_string: #include <bits/stdc++.h>   using namespace std;   long long a[1000000];   int main() {     long long n, s;     cin >> n >> s;     for (long long i = 0; i < n; i++) {       long long k, m;       cin >> k >> m;       a[k] = max(a[k], m);     }     long long ans = 0, last = s;     for (long long i = s; i > 0; i--) {       if (a[i]) {         ans = max(ans + last - i, a[i]);         last = i;       }     }     cout << ans + last;     return 0;   }   