hpgcc2 loop problem

[BINUBALL]

It works properly with zint, thank you for everyone.
And, here is my last source code.

Code:

#include <hpgcc49.h>

int main(void)
{
    // sum 1 to n and counter i
    int n, i;
    int sum = 0;
    // fast mode
    sys_slowOff();
    // get stack 1 zint
    n = sat_pop_zint_llong();
    // calculate sum
    for (i = 1; i <= n; i++) {
        sum += i;
    }
    // output
    sat_push_zint_llong(sum);
    sys_slowOn();
    return(0);
}