Why value is came 4 ? I need 40?

    #include <stdio.h>
    
    int value(int *a);
    
    int main(){
        int num = 4;
        value(&num);
        printf("value of number is = %d", num);
        return 0;
    }

int value(int *a){
    int c = (*a)*10;
    return c;
}

In this code, I transfer the address in function but it does not change, Why?