diff --git a/cv3/program.c b/cv3/program.c
index f0c64a6..5598187 100644
--- a/cv3/program.c
+++ b/cv3/program.c
@@ -24,6 +24,7 @@ int main(void) {
         str[strlen(str) - 1] = 0;
         // if number
         if(strlen(str) > 1 || (str[0] >= '0' && str[0] <= '9')) {
+            my_exit(p_stack->size >= STACK_SIZE, "full stack");
             my_exit(str[0] == '.', "bad input");
             float res = 0.f;
             int dots = 0;