func_code_string: #include <bits/stdc++.h>   using namespace std;   long long a, b, c, d, ans = 0;   const long long maxn = 1e6 + 5;   long long p[maxn];   int main() {     cin >> a >> b >> c >> d;     long long mx = min(b - a, c - b) + 1;     for (long long i = a + b, t = 1; i <= b + c; ++i) {       p[i] = t;       t = min(t + 1, mx);     }     for (long long i = b + c - mx + 1, t = mx; i <= b + c; ++i) {       p[i] = t;       --t;     }     for (long long i = a + b; i <= b + c; ++i) {       p[i] = p[i - 1] + p[i];     }     ans = p[b + c] * (d - c + 1);     for (long long i = c; i <= d; ++i) {       long long ind = min(b + c, i);       ans -= p[ind];     }     cout << ans << endl;   }   