diff --git a/cmd/crt.go b/cmd/crt.go
new file mode 100644
index 0000000..707b60f
--- /dev/null
+++ b/cmd/crt.go
@@ -0,0 +1,114 @@
+/*
+Copyright © 2025 filifa
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+package cmd
+
+import (
+	"fmt"
+	"log"
+	"math/big"
+
+	"github.com/spf13/cobra"
+)
+
+var remainders []string
+var moduli []string
+
+func solveTwo(a1, n1, a2, n2 *big.Int) (*big.Int, *big.Int) {
+	m1 := new(big.Int)
+	m2 := new(big.Int)
+	tmp := new(big.Int)
+	tmp.GCD(m1, m2, n1, n2)
+
+	x := new(big.Int).Set(a1)
+	x.Mul(x, m2)
+	x.Mul(x, n2)
+
+	tmp.Set(a2)
+	tmp.Mul(tmp, m1)
+	tmp.Mul(tmp, n1)
+
+	x.Add(x, tmp)
+
+	N := new(big.Int).Set(n1)
+	N.Mul(N, n2)
+
+	x.Mod(x, N)
+
+	return x, N
+}
+
+func crt(cmd *cobra.Command, args []string) {
+	if len(remainders) != len(moduli) {
+		log.Fatal("number of remainders and moduli do not match")
+	}
+
+	// TODO: check for pairwise comprime
+
+	n1 := new(big.Int)
+	a1 := new(big.Int)
+	for i := range remainders {
+		n2, ok := new(big.Int).SetString(moduli[i], 10)
+		if !ok {
+			log.Fatal("invalid input " + moduli[i])
+		}
+
+		a2, ok := new(big.Int).SetString(remainders[i], 10)
+		if !ok {
+			log.Fatal("invalid input " + remainders[i])
+		}
+
+		if i != 0 {
+			x, N := solveTwo(a1, n1, a2, n2)
+			n1.Set(N)
+			a1.Set(x)
+		} else {
+			a1.Set(a2)
+			n1.Set(n2)
+		}
+	}
+
+	fmt.Println(a1)
+	fmt.Println(n1)
+}
+
+// crtCmd represents the crt command
+var crtCmd = &cobra.Command{
+	Use:   "crt -r R R [R ...] -m M M [M ...]",
+	Short: "Solve a system of linear congruences",
+	Long: `Solve a system of linear congruences.`,
+	Run: crt,
+}
+
+func init() {
+	rootCmd.AddCommand(crtCmd)
+
+	// Here you will define your flags and configuration settings.
+
+	// Cobra supports Persistent Flags which will work for this command
+	// and all subcommands, e.g.:
+	// crtCmd.PersistentFlags().String("foo", "", "A help for foo")
+
+	// Cobra supports local flags which will only run when this command
+	// is called directly, e.g.:
+	// crtCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
+
+	crtCmd.Flags().StringSliceVarP(&remainders, "remainders", "r", make([]string, 0), "remainders of congruences")
+	crtCmd.MarkFlagRequired("remainders")
+
+	crtCmd.Flags().StringSliceVarP(&moduli, "moduli", "m", make([]string, 0), "moduli of congruences")
+	crtCmd.MarkFlagRequired("moduli")
+}