Progressões-[OBI]

#include <stdio.h>
#include <math.h>

int main()
{
        int N,PA[100000], x, base, count=1;

        scanf("%d", &N);

                for(x=0; x<N; x++) {

                        scanf("%d", &PA[x]);  }

                for(x=2; x<N; x++) {

                        base = PA[x-1] - PA[x-2];

                if(PA[x] - PA[x-1] != base) {

                        count++; x=x+1; }

        }

        printf("%d", count);

return 0;
}