//蛇形填数
#include <bits/stdc++.h>

using namespace std;

int main() {
    int m = 20, n = 20, num = 0;
    int cnt = m + n - 1;
    for (int i = 1; i < cnt; ++i) {
        num += i;
    }
    if (cnt % 2 == 0) {
        num += m;
    } else {
        num += n;
    }
    cout << num << endl;
    return 0;
}