diff --git a/du4/.program.c.swp b/du4/.program.c.swp
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Binary files /dev/null and b/du4/.program.c.swp differ
diff --git a/du4/program b/du4/program
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Binary files /dev/null and b/du4/program differ
diff --git a/du4/program.c b/du4/program.c
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--- /dev/null
+++ b/du4/program.c
@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+int main(){
+	int c[2];
+	int a, i = 0;
+	int vysledok;
+	char riadok[999];
+	char *endptr = NULL;
+	bool first = true;
+	bool second = false;
+	while(1){
+		a++;
+		char* r = fgets(riadok,999,stdin);
+		if(*r == '\n'){
+			break;
+		}else if(*r == ' ')
+			continue;
+		else if(*r == '+'){
+			first = true;
+			second = true;;
+			continue;
+		}else if(*r == '-'){
+			first = false;
+			second = false;
+			continue;
+		}else if(*r == '/'){
+			first = true;
+			second = false;
+			continue;
+		}else if(*r == '*'){
+			first = false;
+			second = true;
+			continue;
+		}else{
+			float v = strtod(riadok,&endptr);
+			c[i++] = v;
+			continue;
+		}
+	}
+	if(first == true && second == true)
+		vysledok = c[0] + c[1];
+	else if(first == false && second == false)
+		vysledok = c[0] - c[1];
+	else if(first == true && second == false)
+		vysledok = c[0] / c[1];
+	else if(first == false && second == true)
+		vysledok = c[0] * c[1];
+	if(vysledok == c[2])
+		printf("OK\n");
+	else
+		printf("ZLE\n");
+	return 0;
+}