how to find bug in code

[yeki]

hello everyone
I have a code that is logical but it has error I can't figure it out. can enyone see what the problem is?
Here iss my code:

  #include <iostream>
#include <cmath>
#include <stdio.h>      /* printf */
#include <math.h>       /* ceil */
#define PI 3.141592653589793
using namespace std;




int main()
{

   float N=8;
   float M=8;
   float Q=N;
   float stiff=1;
   float L=2;
   float dx=L/(N-1);//h
   float ds=2;
   float x[8]={1,4,9,0,3,2,7,5};
    float y[8]={1,4,9,0,3,2,7,5};

///////////////////////////////
int i,j;
float force1[8]={0};

force1[0]=(x[1]-2*x[0]+x[7])/pow(ds,2);

for(i=1;i<7;i++){
    force1[i]=(x[i+1]-2*x[i]+x[i-1])/pow(ds,2);

};
force1[7]=(x[0]-2*x[7]+x[6])/pow(ds,2);

float force2[8]={0};
force2[0]=(y[1]-2*y[0]+y[7])/pow(ds,2);
for(i=1;i<7;i++){
    force2[i]=(y[i+1]-2*y[i]+y[i-1])/pow(ds,2);
};
force2[7]=(y[0]-2*y[7]+y[6])/pow(ds,2);
////////////////////////////////////////

float F1[8][8]={0};
float F2[8][8]={0};
for (int i=0,i<=7,i++){
   int x1=ceil((x[i]+1)/dx);
   int x2 =ceil((y[i]+1)/dx);
   for(int k=0,k<=3,k++){
    for(int h=0, h<=3,h++){
            	int ii=x1+1-k %8;
                int jj=x2+1-h %8;
                F1[ii][jj]+=force1[i]*(ds/(16*power(dx,2))*(1+cos((PI/(2*dx))*(dx*(x1+1-k)-x[i])))*(1+cos((PI/(2*dx))*(dx*(x2+1-h)-y[i])));

   };
   };

};
return{0};


}

thank you
Yeki

[giblit]

what exactly is the problem? Also your code is very ill-formated and very hard to read. You should invest into symbolic names I think it is called ex:
if you have a variable used for getting height you should declare it like
int height; versus int iijk; There is a word for naming variables like that but I honestly forgot what it is called. I would indenting properly also to fix the ill-formation.