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#include <bits/stdc++.h>
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#define ll long long
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using namespace std;
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int main() {
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    std::ios_base::sync_with_stdio(false);
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    cin.tie(0);
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    cout.tie(0);
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    int n;
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    cin >> n;
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    int cost[n + 1] = {};
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    for (int i = 1; i <= n; ++i) {
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        cin >> cost[i];
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    }
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    int dp[n + 1] = {};
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    dp[0] = 0;
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    dp[1] = dp[0] + cost[1];
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    for (int i = 2; i <= n; ++i) {
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        dp[i] = min(dp[i - 1], dp[i - 2]) + cost[i];    
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    }
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    cout << dp[n];
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    return 0;
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}
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