Problems

# Cost of call

# Cost of call

Find the cost of a phone call in kopecks with duration of **n** seconds, if the connecting cost is **a** kop., the tariffication is per minute, that is the first second of each minute is charged to pay **b** kop.

#### Input

Three non-negative integers **a**, **b** and **n** (**0** ≤ **a**, **b** ≤ **99**, **0** ≤ **n** ≤ **86400**).

#### Output

Print the cost of a phone call in kopecks.

Input example #1

5 10 120

Output example #1

25