It is probably the most famous alphametic in mathematical recreation: a verbal sum that looks like a toy and ends up functioning as a chain deduction.
SEND MORE MONEY
Riddle statement
A young mathematician, son of a mathematician, writes to his father to ask for money, but decides to do it his own way. Instead of writing the amount directly, he sends him this sum:
\begin{array}{r}
\texttt{SEND} \\
+\,\texttt{MORE} \\
\hline
\texttt{MONEY}
\end{array}
Each letter represents a different digit from 0 to 9, and no word can start with 0.
How much money does he send?