Convert char String to an int but not possible to convert a char from an char string to an int?

Question

char input[5] = "12345";

printf("Convert to int valid %d", atoi(input));
printf("Convert to int invalid %d", atoi(input[1])); // program crash

Is there a solution to convert an char "slice" of an char string into an int? Short description:

User inputs a string with values for example: 1, 2 3 4 ,5 Iam formating that string to 12345 With each number i want to continue to work with the index of an array.