void rstrct(double **uc, double **uf, int nc)
{
	int ic,iif,jc,jf,ncc=2*nc-1;

	for (jf=3,jc=2;jc<nc;jc++,jf+=2) {
		for (iif=3,ic=2;ic<nc;ic++,iif+=2) {
			uc[ic][jc]=0.5*uf[iif][jf]+0.125*(uf[iif+1][jf]+uf[iif-1][jf]
					+uf[iif][jf+1]+uf[iif][jf-1]);
		}
	}
	for (jc=1,ic=1;ic<=nc;ic++,jc+=2) {
		uc[ic][1]=uf[jc][1];
		uc[ic][nc]=uf[jc][ncc];
	}
	for (jc=1,ic=1;ic<=nc;ic++,jc+=2) {
		uc[1][ic]=uf[1][jc];
		uc[nc][ic]=uf[ncc][jc];
	}
}