Resistors in Series or Parallel

Easy#engineering #electronics· solved by 0 · time limit 2.0 s

Series resistors add: $R = R_1 + R_2 + \dots$ . Parallel resistors add as reciprocals: $\frac1R = \frac1{R_1} + \frac1{R_2} + \dots$ . Print the total resistance with 2 decimals.

Input

Line 1: series or parallel. Line 2: $n$ followed by $n$ resistances in ohms.

Output

The total resistance.

Constraints

$1 \le n \le 1000$ , each $R_i$ between 1 and $10^6$ Ω.

Sample 1

Input

series
3 100 220 330

Output

650.00

Sample 2

Input

parallel
2 1000 1000

Output

500.00