#include <stdio.h> int main() { int n; double sum = 0; scanf("%d",&n); for(int i = 1 ; i <= n ; i++) { int p = 1; double down_sum = 0; for(int j = 1 ; j <= 2 * i - 1 ; j += 2) { down_sum = down_sum + (j * p); p = -p; } sum += 1 / down_sum; } printf("%.3f",sum); return 0; }
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