diff --git a/du4/program b/du4/program
new file mode 100644
index 0000000..bd51f49
Binary files /dev/null and b/du4/program differ
diff --git a/du4/program.c b/du4/program.c
new file mode 100644
index 0000000..dcba597
--- /dev/null
+++ b/du4/program.c
@@ -0,0 +1,140 @@
+#include<stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include<math.h>
+#include <string.h>
+
+struct priklad//vytvorenie štruktúry, typu, v ktorom existujú iné typy
+{
+ double one;
+ char znak;
+ double two;
+ double sum;
+};
+
+int sort(struct priklad prik[20]);
+void printAll(struct priklad prik[20], int i);
+
+int main(){
+
+struct priklad prik[20];
+int i = sort(prik);
+
+printAll(prik,i);
+
+ return 0;
+}
+void printAll(struct priklad prik[20], int i){
+    for (size_t j = 0; j < i; j++)
+{
+if( prik[j].one == 0 && prik[j].two == 0 &&prik[j].sum == 0){
+    printf("CHYBA\n");
+    continue;
+}
+ if(prik[j].znak == '+'){
+  // printf("%f", prik[j].one + prik[j].two);
+  if (round((prik[j].one + prik[j].two)*100)/100 == prik[j].sum)// round-zaokrúhli číslo
+  {
+   printf("OK\n");
+  } else
+  {
+   printf("ZLE\n");
+  }
+  
+ }
+ if(prik[j].znak == '-'){
+  if (round((prik[j].one - prik[j].two)*100)/100 == prik[j].sum)
+  {
+   printf("OK\n");
+  } else
+  {
+   printf("ZLE\n");
+  }
+  
+ }
+ if(prik[j].znak == '*'){
+  if (round(prik[j].one * prik[j].two * 100) / 100 == prik[j].sum)
+  {
+   printf("OK\n");
+  } else
+  {
+   printf("ZLE\n");
+  }
+  
+ }
+ if(prik[j].znak == '/'){
+  if (round(prik[j].one / prik[j].two * 100) / 100 == prik[j].sum)
+  {
+   printf("OK\n");
+  } else
+  {
+   printf("ZLE\n");
+  }
+  
+ }
+
+}
+}
+
+int sort(struct priklad prik[20]){
+int i = 0; 
+    while (1)
+    {
+        char step_line[30];
+        char step_one[5];
+        memset(step_one,' ',5);//vyplnenie štandardnými hodnotami poľa
+        char step_two[10];
+        memset(step_two,' ',10);
+        char step_sum[10];
+        memset(step_sum,' ',10);
+        char* r = fgets(step_line,30,stdin);    //číta koncový znak
+        if (r == NULL){
+            break;
+        }
+        int k = 0;
+        while (step_line[k] != ' ')
+        {
+        step_one[k] = step_line[k]; 
+        k++;
+        }
+        k++;
+        prik[i].znak = step_line[k];
+        k = k+2;
+        int j = 0;
+        while (step_line[k]!= ' ')
+        {
+            step_two[j] = step_line[k];
+            k++;
+            j++;
+        }
+
+
+        k = k+3;
+        int p = 0;
+        while (k<strlen(step_line)-1)//dĺžka linky
+        {
+            
+            step_sum[p] = step_line[k];
+            k++;
+            p++;
+            
+        }if (isalpha(step_one[0])|| isalpha(step_two[0])|| isalpha(step_sum[0]))//isalpha-vráti hodnotu true, ak je vstupný argument z abecedy
+        {
+            prik[i].one = 0;
+            prik[i].two = 0;
+            prik[i].sum = 0;
+        }else{
+        
+            prik[i].one = atof(step_one);//vytvorí číslo z radu kúziel
+            prik[i].two = atof(step_two);
+            prik[i].sum = atof(step_sum);
+        }
+        if (step_line[0] == '\n')
+        {
+            i--;
+        }
+        
+    i++;
+    }
+    return i;
+}