diff --git a/du4/program.c b/du4/program.c
index 9c423a9..e50a49e 100644
--- a/du4/program.c
+++ b/du4/program.c
@@ -23,7 +23,7 @@ int main(){
 
     float num2=strtof(start,&end);
 	start=end;
-    while((*start)<'0'||(*start)>'9'||(*start)!='-'){
+    while(((*start)<'0'||(*start)>'9')&&(*start)!='-'){
         start++;
     }