Need solution of "The River 1" in C

Puzzles
#1

Can anyone provide the solution of challenge “the river 1” in C or C++. I am gonna be honest I am lost and I cant figure out shit.

#2

there are plenty of hints here:
https://www.codingame.com/forum/t/the-river-i/34563

I suggest trying other easy puzzles if you’re blocked on this one

#3
#4