diff --git a/c/sum_K_O_n/sum_k_o_n.c b/c/sum_K_O_n/sum_k_o_n.c
new file mode 100644
index 0000000..d77b408
--- /dev/null
+++ b/c/sum_K_O_n/sum_k_o_n.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+int input[] = {5,1,8,6,9,2,44,3,31,26,36,47,51,72,88,7,4};
+int N=sizeof(input)/sizeof(int);
+int K = 10; 
+void print_pair(int *input,int K) {
+        int *mem=alloca(sizeof(int)*K);
+        int t,i;
+        memset(mem,0,sizeof(int)*K);
+        for(t=0;t<N;t++) {
+                i=input[t];
+                if (i<=0 || i>=K) continue;
+                if (mem[K-i]!=0) {
+                        printf("%d %d\n",i,K-i);
+                        mem[K-i]=0;
+                } else
+                        mem[i]=1;
+        }   
+}
+int main() {
+        print_pair(input,K);
+        return 0;
+}
+
+