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class Solution {
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 public:
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  int sumSubarrayMins(vector<int> &n) {
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    vector<long> s, sums(n.size(), 0);
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    long j, res = 0, mod = 1000000007;
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    for (int i = 0; i < n.size(); ++i) {
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      while (!s.empty() && n[s.back()] > n[i]) s.pop_back();
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      j = !s.empty() ? s.back() : -1;
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      sums[i] = ((j >= 0 ? sums[j] : 0) + (i - j) * n[i]) % mod;
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      s.push_back(i);
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    }
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    for (int i = 0; i < sums.size(); ++i) res = (res + sums[i]) % mod;
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    return res;
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  }
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};