#pragma once
#include <stddef.h>
#include <stdarg.h>
/* The interpreter only uses %s, %c, %d and %zu. No device stdio required. */
typedef void FILE;
#define stdin ((FILE *)0)
#define stderr ((FILE *)0)
#define EOF (-1)
static int vsnprintf(char *dst, size_t cap, const char *fmt, va_list ap) {
    size_t n = 0;
#define EMIT(c) do { char emitted = (c); if (n + 1 < cap) dst[n] = emitted; ++n; } while (0)
    while (*fmt) {
        if (*fmt != '%') { EMIT(*fmt++); continue; }
        ++fmt;
        if (*fmt == 's') {
            const char *s = va_arg(ap, const char *);
            while (*s) { EMIT(*s++); }
        } else if (*fmt == 'c') {
            char c = (char)va_arg(ap, int); EMIT(c);
        } else {
            unsigned v;
            if (*fmt == 'z') { ++fmt; v = (unsigned)va_arg(ap, size_t); }
            else {
                int value = va_arg(ap, int);
                v = (unsigned)value;
                if (value < 0) { EMIT('-'); v = 0u - v; }
            }
            char digits[10]; unsigned count = 0;
            do { digits[count++] = '0' + v % 10; v /= 10; } while (v);
            while (count) { char c = digits[--count]; EMIT(c); }
        }
        ++fmt;
    }
    if (cap) dst[n < cap ? n : cap - 1] = 0;
#undef EMIT
    return (int)n;
}
static int snprintf(char *dst, size_t cap, const char *fmt, ...) {
    va_list ap; va_start(ap, fmt);
    int n = vsnprintf(dst, cap, fmt, ap);
    va_end(ap); return n;
}

static int isdigit(int c) { return c >= '0' && c <= '9'; }
static int isalpha(int c) { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'); }
static int isalnum(int c) { return isalpha(c) || isdigit(c); }