using namespace std;
#include <bits/stdc++.h>
 
long long getPrefSum(int n) {
    return 1LL * n * (n + 1) / 2;
}
 
int main() {
    ios::sync_with_stdio(false);
    cout.tie(nullptr), cin.tie(nullptr);
 
    int n, m;
    cin >> n >> m;
 
    int k = min(m - 2, n - 1);
    long long rows = getPrefSum(m - 2) - getPrefSum((m - 2) - k);
 
    long long columns = getPrefSum(n - 1);
    if (n >= m) columns -= getPrefSum((n - 1) - (k + 1));
    else columns -= getPrefSum((n - 1) - k);
 
    cout << columns + rows << endl;
 
    return 0;
}

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OTk5OTk5OTk5IDk5OTk5OTk5OA==

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