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

int main()
{
    int k;
    int rslt = 0;
    char line[200];

    scanf("%d%s", &k, line);

    for (int i = (int) strlen(line) -1 ; i >= 0 ; i--)
    {
        if (line[i] - '0' >= 0 && line[i] - '0' <= 9)
            rslt += (int) pow(k, (int) strlen(line) - i - 1) * (line[i]-'0');
        else
            rslt += (int) pow(k, (int) strlen(line) - i - 1) * (line[i]-'a' + 10);
    }

    printf("%d", rslt);

    return 0;
}