func_code_string: #include <bits/stdc++.h>   using namespace std;   int num[300005][2];   int jichu = 100000;   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int n, m, x;     cin >> n >> m;     if (n == 1) {       cout << 0 << endl;       return 0;     }     long long cont = 0, sum = n;     for (int i = 1; i <= n; i++) {       num[jichu + i][0] = 1;       num[jichu + i][1] = 1;     }     for (int i = 1; i <= m; i++) {       cin >> x;       int l = x - i, r = x + i;       if (num[jichu + l][1] > 0) {         cont += 1LL * num[jichu + l][1];         num[jichu + l - 1][1] += num[jichu + l][1];         num[jichu + l][1] = 0;       }       if (num[jichu + r][0] > 0) {         cont += 1LL * num[jichu + r][0];         num[jichu + r + 1][0] += num[jichu + r][0];         num[jichu + r][0] = 0;       }     }     for (int i = jichu + 1 - m; i < jichu + n; i++) {       if (i + m + 1 > jichu + n) {         sum += 1LL * num[i][1] * ((m + 1) - (i + m + 1 - jichu - n));       } else {         sum += 1LL * num[i][1] * (m + 1);       }     }     for (int i = jichu + 2; i <= jichu + n + m; i++) {       if (i <= jichu + m + 1) {         sum += 1LL * num[i][0] * (i - jichu - 1);       } else {         sum += 1LL * num[i][0] * (m + 1);       }     }     sum -= cont;     cout << sum << endl;     return 0;   }   