Measurements of the branching fractions for $D^{+}\to K_S^0{K}_S^0{K}^{+}$, $K_S^0{K}_S^0{\pi }^{+}$ and $D^0\to K_S^0{K}_S^0$, $K_S^0{K}_S^0{K}_S^0$

By analyzing $2.93\mathrm{f}{\mathrm{b}}^{-1}$ of data taken at the $\psi (3770)$ resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays $D^{+}\to K_S^0{K}_S^0{K}^{+}$, $D^{+}\to K_S^0{K}_S^0{\pi }^{+}$, $D^0\to K^0_S K^0_S$and$D^0\to K^0_SK^0_SK^0_S$\mathrm{.}Theyaredeterminedtobe${\mathcal B}(D^+\to K^0_SK^0_SK^+)=(2.54 \pm 0.05_{\rm stat.} \pm 0.12_{\rm sys.})\times 10^{-3}$,${\mathcal B}(D^+\to K^0_SK^0_S\pi^+)=(2.70 \pm 0.05_{\rm stat.} \pm 0.12_{\rm sys.})\times 10^{-3}$,${\mathcal B}(D^0\to K^0_SK^0_S)=(1.67 \pm 0.11_{\rm stat.} \pm 0.11_{\rm sys.})\times 10^{-4}$and${\mathcal B}(D^0\to K^0_SK^0_SK^0_S)=(7.21 \pm 0.33_{\rm stat.} \pm 0.44_{\rm sys.})\times 10^{-4}$, where the second one is measured for the first time and the others are measured with significantly improved precision over the previous measurements.