fibunacci (primitive recursive)

#include <stdio.h>
#include <stdlib.h>

int main( int argc, char *argv[] )
{
    int in = atoi(argv[1]) - 2;
    int i = 0;
    int prev = 1;
    int prevprev = 0;
    int cur = 0;
    if (-1 < in) {
        cur = 1;
    }
    while (i < in) {
        cur = prev + prevprev;
        prevprev = prev;
        prev = cur;
        ++i;
    }
    printf("%d\n", cur);

    return 0;
}