func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     set<int> keyboards;     scanf( %d , &n);     for (int i = 0; i < n; i++) {       int a;       scanf( %d , &a);       keyboards.insert(a);     }     int prev = 0;     int result = 0;     for (auto keyboard : keyboards) {       if (prev != 0) result += (keyboard - prev - 1);       prev = keyboard;     }     printf( %d n , result);   }   