Nearest Strong City

During world war $1$, there were $N$ cities and $M$ roads connecting cities in a country. Each $j^{th}$ road in the country is of particular distance $D_j$ and each $i^{th}$ city has population $A_i$. There was a secret message of the enemy intercepted which tells that enemy is going to attack the roads of the country. If an enemy attacks a particular road then that road becomes unusable. Let us