#include <stdint.h>
#include <assert.h>
extern int64_t backtest_step(int64_t state, int64_t sample);
int main(void) {
    int64_t s = 0;
    s = backtest_step(s, 3);   /* 0 + 9  */
    s = backtest_step(s, 4);   /* 9 + 16 */
    assert(s == 25);
    return 0;
}