Waterloo 2022 Fall A - Zero AAMP Currents
View as PDF2022 Fall Waterloo Local Contest, Problem A
Thomas Edison stumbled upon an alien electrical device that appears to break known laws of physics!
The device consists of  batteries connected by 
 unidirectional wires, which we will represent as vertices
and edges that form a graph. The 
 wire is directed from battery 
 to battery 
, 
. Let 
denote such a wire.
To make this device work, Thomas must assign a current strength to each wire such that this assignment results in a successful configuration. For a configuration to be successful, two conditions must be met:
- All current strength values are non-zero integers in the range 
AAMP (Alien Amperes).
 - For every cycle found in this device, the sum of AAMP values from all wires in it must be 
. A cycle is a sequence of edges (wires)
. If edges
and
both exist, they also form a cycle - the wires are unidirectional.
 
Help him with this task.
Constraints
Input Specification
The first line contains two integers  and 
 - the number of batteries and the number of wires in the
device, respectively. Next, 
 lines contain two integers each 
 and 
, which mean that the 
 wire goes
from battery 
 to 
.
Output Specification
Print  lines containing one number each: the 
 number should be the current strength of 
 wire (in
AAMP). Each number should be non-zero and in the range of 
. If multiple answers exist,
you may print any one of them.
Sample Input
4 7
1 2
2 3
3 1
1 4
2 4
1 4
3 2
Sample Output
-1
-1
2
-2
-1
-2
1
Note
Note that there can be multiple wires from battery  to 
. Also note that wire 
 with strength 
AAMP is not the same as 
 with strength 
. As mentioned before, wires are unidirectional and
can have a negative current strength - that's one of the mysteries of this device…
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