In 1 km races, runner 1 on track 1 (with time $2 \min .27 .95 \mathrm{~s}$ ) appears to be faster than runner 2 on track $2(2 \min , 28.15 \mathrm{~s})$. Howcver, length $L_{2}$ of track 2 might be slightly greater than length $L_{1}$ of track 1. How large $\operatorname{can} L_{2}-L_{1}$ be for us still to conclude that runner 1 is faster?