func_code_string: #include <bits/stdc++.h>   using namespace std;   void solve() {     long long n, k;     cin >> n >> k;     if (n >= k) {       cout << (k - 1) / 2 << endl;     } else if (k - n > n) {       cout <<  0  << endl;     } else {       cout << (n - (k - n) + 1) / 2 << endl;     }   }   int main() {     solve();     return 0;   }   