Do you like puzzles?Euler did.Did you solve the one you heard for the lisening task? No!Well,don't worry,Euler didn't either!As he loved mathematical puzzles,he wanted to know why this one woudn't work.So he walked around the town and over the bridges of Kongsberg several times.To his surprise,he found that he could cross six of the bridges without going over any of them twice or going back on himself(see Fig 3),but he couldn't cross all seven.He just had to know why.So he decided to look at the problem another way.