diff --git a/du4/program.c b/du4/program.c
new file mode 100644
index 0000000..ea71802
--- /dev/null
+++ b/du4/program.c
@@ -0,0 +1,158 @@
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+char array[100];
+char array1[100];
+char number1[100];
+char number2[100];
+char answer[100];
+int p=0;
+float zero=0;
+char znak1;
+char znak2;
+float firstN=0;
+float secondN=0;
+float answer1=0;
+float myAnswer=0;
+char c;
+char r;
+char q;
+int count = 0;
+int scan(char* array2){
+char* r = fgets(array1,100,stdin);
+if (r == NULL){
+        return -1;
+}
+        else{
+        return 0;
+        }
+}
+int main(){
+scan(array1);
+int i=0;
+while(i<100){
+        i=i+1;
+        if(array1[i]!='\n'){
+	        count=count+1;
+	}	
+        if(array1[i]=='\n'){	
+	        if(array1[i+1]=='\n')
+		{ 
+		array1[i]='#';
+		break;
+		}
+	}
+        else
+	{
+	count=count+1;
+	}
+}
+i=0;
+int j=0;
+int t=0;
+while(array1[t]!='#'){
+        array[p]=array1[t];
+        if(array1[t]=='='){
+	t=t+1;
+	p=p+1;
+	if(array1[t]==' '){
+		array[p]=array1[t];
+		t=t+1;
+		p=p+1;
+		}
+	while(array1[t]!=' ')
+		{
+		if(array1[t]=='#'){
+                        break;
+                        }
+		        array[p]=array1[t];
+		        t=t+1;
+		        p=p+1;
+		        }
+                while(array[i]!='\0'){
+	                if(array[i]=='+'||array[i]=='-'||array[i]=='/'||array[i]=='*'){
+	                        break;
+	                }
+	                else if(array[i]=='1'||array[i]=='2'||array[i]=='3'||array[i]=='4'||array[i]=='5'||array[i]=='6'||array[i]=='7'||array[i]=='8'||array[i]=='9'||array[i]=='0'||array[i]=='.'){
+	                        number1[j]= array[i];
+	                        i=i+1;
+	                        j=j+1;
+	                }
+	                else if(array[i]==' ' || isalpha(array[i])){i++;}
+	                        else{
+	                        printf("CHYBA\n");
+	                        return 0;
+	                        }
+                        }
+                znak1=array[i];
+                i=i+1;
+                j=0;
+                while(array[i]!='='){
+                        if(array[i]=='1'||array[i]=='2'||array[i]=='3'||array[i]=='4'||array[i]=='5'||array[i]=='6'||array[i]=='7'||array[i]=='8'||array[i]=='9'||array[i]=='0'||array[i]=='.'){
+                                number2[j]=array[i];
+                                j=j+1;
+	                        i=i+1;
+                        }
+	else if(array[i]==' '){
+                i=i+1;
+                }
+        else{
+                i=i+1;
+                p=p+1;
+        }
+}
+        znak2=array[i];
+        i++;
+        j=0;
+        j=0;
+while(array[i]=='1'||array[i]=='2'||array[i]=='3'||array[i]=='4'||array[i]=='5'||array[i]=='6'||array[i]=='7'||array[i]=='8'||array[i]=='9'||array[i]=='0'||array[i]==' '||array[i]=='.'){
+        if(array[i]=='1'||array[i]=='2'||array[i]=='3'||array[i]=='4'||array[i]=='5'||array[i]=='6'||array[i]=='7'||array[i]=='8'||array[i]=='9'||array[i]=='0'||array[i]=='.'){
+        answer[j]=array[i];
+        i=i+1;
+	j=j+1;
+        }
+	else if(array[i]==' '){
+                i=i+1;
+        }else{
+                i=i+1;
+                p=p+1;
+                }
+        }
+        j=0;
+        float firstN = atof(number1);
+        float secondN = atof(number2); 
+        float answer1 = atof(answer);
+        if(znak1=='-'){
+                myAnswer=firstN-secondN;
+        }
+        else if(znak1=='+'){
+                myAnswer=firstN+secondN;
+        }
+        else if(znak1=='/'){
+                myAnswer=firstN/secondN;
+        }
+        else if(znak1=='*'){
+                myAnswer=firstN*secondN;
+        }
+                zero = myAnswer-answer1;
+        if(zero>=-0.00001&&zero<=0.00001){
+        printf("OK\n");
+        }
+        else{
+                printf("ZLE\n");
+        }
+        i=0;
+        p=-1; 
+        memset(array,0,100);
+        }
+        p=p+1;
+        t=t+1;
+        scanf("\n%c",&q);
+        if(c=='\n'){
+        return 0;
+        }
+}
+        return 0;
+}
\ No newline at end of file