Scientists are studying biological cycles in organisms. Each organism has a cycle with a specific period and a target phase.

Given n organisms, each with a period p[i] and target phase t[i], find the earliest time T (T ≥ 0) when ALL organisms simultaneously reach their target phases.

An organism with period p and target phase t is at its target phase at time T if: T mod p == t

If no such time exists, return -1.

The first line contains an integer n, the number of organisms. The next n lines each contain two integers: period and target_phase.

Print the earliest time T, or -1 if impossible.