- Time limit: 1.00 s
- Memory limit: 512 MB
Your task is to process $q$ queries of the form: "after how many days can we travel from city $a$ to city $b$ for the first time?"
The first input line has three integers $n$, $m$ and $q$: the number of cities, roads and queries. The cities are numbered $1,2,\dots,n$.
After this, there are $m$ lines that describe the roads in the order they are built. Each line has two integers $a$ and $b$: there will be a road between cities $a$ and $b$.
Finally, there are $q$ lines that describe the queries. Each line has two integers $a$ and $b$: we want to travel from city $a$ to city $b$.
For each query, print the number of days, or $-1$ if it is never possible.
- $1 \le n, m, q \le 2 \cdot 10^5$
- $1 \le a,b \le n$
5 4 3