std

#include <stdio.h>

int main() {
    int n; scanf("%d", &n);
    double ans = 1.0;
    int i; double cnt;
    for(i = 2; i <= n; i++) {
        cnt = 1.0/i;
        if(i%2 == 0) ans -= cnt;
        else ans += cnt;
    }
    printf("%.2lf\n", ans);
    return 0;
}