func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, f;   long long ans;   long long k, l;   long long d[100001];   int main() {     cin >> n >> f;     for (int i = 1; i <= n; i++) {       cin >> k >> l;       d[i] = -min(k, l - k);       ans = ans + min(k, l);     }     sort(d + 1, d + n + 1);     for (int i = 1; i <= f; i++) ans = ans + max(-d[i], (long long)(0));     cout << ans;     return 0;   }   