#include <stdio.h>
#include <stdarg.h>
int prefix_printf(const char* fmt, ...)
{
    printf("prefix ");

    va_list args;
    va_start(args, fmt);

    int result = vprintf(fmt, args);
    va_end(args);
    return result;
}


int main(void) {
	prefix_printf("No number\n");
    prefix_printf("Number = %d\n", 20);
    return 0;
}