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1sem/programming basics/z5/15.cpp

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+// pb_z5_15.cpp
+// Горбацевич Андрей
+#include <iostream>
+using namespace std;
+
+double ai(int);
+double s(int);
+
+int main() {
+    int N;
+    cout << "N >>>";
+    cin >> N;
+    cout << "S= " << ai(N);
+}
+
+double ai(int N) {
+    double out = 0;
+    for (int i = 1; i <= N; i++)
+        out += i * s(i);
+    return out;
+}
+
+double s(int i) {
+    return (i % 2? -1 : 1);
+}