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518D - Ilya and Escalator
https://codeforces.com/contest/518/submission/173706602
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Codeforces/518/D/D.cpp
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37
Codeforces/518/D/D.cpp
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#include <iostream>
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#include <iomanip>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 2005;
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int n, t;
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double p, f[N][N], ans;
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> p >> t;
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f[0][0] = 1;
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for (int i = 1; i <= t; i++) {
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f[i][0] = (1.0 - p) * f[i - 1][0];
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for (int j = 1; j < n; j++) {
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f[i][j] = p * f[i - 1][j - 1] + (1.0 - p) * f[i - 1][j];
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}
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f[i][n] = f[i - 1][n] + p * f[i - 1][n - 1];
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}
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for (int i = 1; i <= n; i++) {
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ans += f[t][i] * i;
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}
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cout << std::fixed << std::setprecision(6) << ans << endl;
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return 0;
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}
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