6digits

#include <stdio.h>

unsigned long charToInt(char c) {
    switch (c) {
        case '0': return 0;
        case '1': return 1;
        case '2': return 2;
        case '3': return 3;
        case '4': return 4;
        case '5': return 5;
        case '6': return 6;
        case '7': return 7;
        case '8': return 8;
        case '9': return 9;
    }
}

int main(void) {
    unsigned long total = 0;

    for (int i = 0; i < 6; ++i) {
        total = total * 10 + charToInt(getchar());
    }

    printf("You entered number: %d\n", total);
}