#include 
                    int sum(int a,int b);
                    int subtract(int a,int b);
                    int multiply(int a,int b);
                    float divide(float a,float b);
                    int modulus(int a,int b);
                    int main()
                    {
                      int num_1,num_2,choice,result;
                      float result_division;
                      char continu;
                      printf("MENU:\t1.add\t2.subtract\t3.multiply\t4.divide\t5.modulus\n");
                      do{
                        prinf("Enter your choice: ");
                        scanf("%dt",&choice);
                        printf("Enter your two numbers:\n");
                        scanf("%d%d",&num_1,&num_2);
                        switch(choice){
                            case 1:
                                result=sum(num_1,num_2);
                                printf("result=%d\n",result);
                                break;
                            case 2:
                                result=subtract(num_1,num_2);
                                printf("result=%d\n",result);
                                break;
                            case 3:
                                result=multiply(num_1,num_2);
                                printf("result=%d\n",result);
                                break;
                            case 4:
                                if(num_2!=0){
                                result_division=divide(num_1,num_2);
                                printf("result=%f\n",result_division);}
                            else
                                printf("un known\n");    
                                break;
                            case 5:
                                result=modulus(num_1,num_2);
                                printf("result=%d\n",result);   
                                break;
                            default:
                                printf("enter {1,2,3,4,5}\n");	    
                        }
                        printf("enter y to continue:");
                        scanf(" %c",&continu);
                    }while(continu=='y'||continu=='Y');			    
                        
                    return 0;
                    }
                    
                    int sum(int a,int b){
                      return a+b;
                    }
                    int subtract(int a,int b){
                      return a-b;
                    }
                    int multiply(int a,int b){
                      return a*b;
                    }
                    float divide(float a,float b){
                      return a/b;
                    }
                    int modulus(int a,int b){
                      return a%b;
                    }