Fiddling with for statement

At times fiddling with C programs and syntax can be real fun. Following is a simple program in C, which currently is not working

#include <stdio.h>
int main(int argc, char *argv[])
{
    int i, n = 20;
    for ( i = 0; i < n; i--)
        printf("-");
    return 0;
}

You can change one character in the above program to make it working. There are three such solutions existing. So have fun with the C syntax and more than one way to accomplish task.