base 26 uppercase alpha string to integer

ualpha26_to_int.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int ipow(int base, int exp)
{
    int r = 1;
    while (exp) {
        if (exp & 1)
            r *= base;
        exp >>= 1;
        base *= base;
    }
    return r;
}

int seed2int(const char *c)
{
    int t = 0;
    size_t ln = strlen(c);
    for (int i = 0; i < ln; ++i)
        t += ipow(26, ln - 1 - i) * (c[i] - '@');
    return t;
}

int main(void)
{
    const char *c = "A";
    printf("%d\n", seed2int(c));
    return 1;
}