740 统计数字字符个数
输入一行字符，统计出其中数字字符的个数。
一行字符串，总长度不超过255。
输出为1行，输出字符串里面数字字符的个数。
Peking University is set up at 1898.
4
Tom was born in 2010, and he is 10 years old.
6
输入一行字符，统计出其中数字字符的个数。
Peking University is set up at 1898.
4
Tom was born in 2010, and he is 10 years old.
6