func_code_string: #include <bits/stdc++.h>   const int INF = 0x3f3f3f3f;   using namespace std;   const int N = 1000100;   bool isp[N];   void prep() {     for (int(i) = (2); (i) < (N); ++(i)) isp[i] = true;     for (int i = 2; i * i < N; i++)       if (isp[i])         for (int j = i * i; j < N; j += i) isp[j] = false;   }   int a, b, k;   bool f(int len) {     if (len > b - a + 1) return false;     int np = 0;     for (int i = 0; i < len; i++) np += isp[a + i];     if (np < k) return false;     for (int i = a + len; i <= b; i++) {       np -= isp[i - len];       np += isp[i];       if (np < k) return false;     }     return true;   }   int main() {     ios::sync_with_stdio(false);     prep();     cin >> a >> b >> k;     int lo = 1, hi = b - a + 2;     while (lo != hi) {       int mi = (lo + hi) / 2;       if (f(mi))         hi = mi;       else         lo = mi + 1;     }     if (lo == 0 || lo > b - a + 1) lo = -1;     cout << lo <<   n ;     return 0;   }   