format ‘%d’ expects argument of type ‘int’, but argument 2 has type

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
int main()
{
    int fd[2];
    size_t size=0;
    char str[] = "a";
    char resstring[2];
    long i=0;
    if(pipe(fd) < 0)
    {
        printf("Can\'t create pipe\n");
        return -1;
    }
    while (size!=-1)
    {
    i++;
    size = write(fd[1], str, 1);
    printf("size: +%d byte, %d bytes total\n",size, i);
    }
    size = read(fd[0], resstring, 2);
    printf("%s\n",resstring);
    close(fd[1]);
    close(fd[0]);
    return 0;
}

printf("size: +%d byte, %d bytes total\n", (int)size, i);