dumb_sum.c

#include <stdio.h>

int
discover_value(int value)
{
    if (value >= '0' && value <= '9') {
        return value - '0';
    }
    return value;
}

int
dumb_sum(int x, int y)
{
    return discover_value(x) + discover_value(y);
}

int
main(void)
{
    printf("%d\n", dumb_sum('2', 2));
    printf("%d\n", dumb_sum(50, 2));
    return 0;
}