I have a file with the following content
123456789,123
234567891,345
345678901,234
124356877,456
I have to read these data and check the validity
the following conditions must be satisfied:
1. there is one and only one comma
2. all symbols except comma are digits(0-9)
3. there are exactly 13 digits before comma
I cannot figure out the method, please help!! thank you
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