func_code_string: #include <bits/stdc++.h>   int main() {     long n, m;     scanf( %ld %ld , &n, &m);     std::vector<long> a(n + 2, 0);     a[n + 1] = m;     for (long p = 1; p <= n; p++) {       scanf( %ld , &a[p]);     }     long orig(0), off(0), mx(0);     for (long p = n; p >= 0; p--) {       if (p % 2) {         off += a[p + 1] - a[p];       } else {         orig += a[p + 1] - a[p];       }       mx = (mx > off - orig) ? mx : (off - orig);     }     printf( %ld n , orig + (mx > 0) * (mx - 1));     return 0;   }   