so i was solving https://codeforces.net/contest/1138/problem/E. the idea here is quite obvious. compress all SCC as a single node and solve it like a normal DAG

then something strange happening. at the beginning i got a RTE verdict for my solution. when i was trying to find bugs in my code, i tried to reverse engineer and add this code my first DFS function (i used kosaraju's algorithm) :

if(n == 99998 && m == 99999 && d == 50) { if(u.fi > 100000 || u.se > 50) { cout << "KOSA : " << u.fi << " " << u.se << "\n"; fflush(stdout); } } magically, adding this piece of code to my solution give me an AC verdict.

RTE solution : https://codeforces.net/contest/1138/submission/51269031

AC solution : https://codeforces.net/contest/1138/submission/51268839

so what really happened? is there any error in CF?