#include<stdio.h>
#include<string>
char keyad[10][5]={
    ""
    ,
    ""
    ,
    "ABC",
    "DEF",
    "GHI",
    "JKL",
    "MNO",
    "PQRS",
    "TUV",
    "WXYZ"
};
void generate(char digits[],int index, char result[]){
    if(digits[index] =='\0'){
        printf("%s\n",result);
        return;
    }
    int digit = digits[index]-'0';
    for(int i = 0; keypad[digit][i] !='\0';i++){
        result[index]=keypad[digit][i];
    }
}
int main(){
    char digits[20];
    printf("enter digits:");
    scanf("%s",digits);
    char result[20];
    printf("possible combination:\n");
    generate(digits,0,result);
    return 0;
}