#include<stdio.h>
#include<string.h>

char*keys[]={"","","ABC","DEF","GHI","JKL","MNO","PQRS","TUV","WXYZ"};
void (char*digits,char*output,ind idx){
    if(!digits[idx]){
        printf("%s",output);
        return;
    }
    int d=digits[idx]-'0';
    if(d<2||d>9){
        printf("Invalid input");
        return;
    }
    for(int i=0;keys[d][i];i++){
        output[idx]=keys[d][i];
    }
}
int main(){
    char digits[20],output[20];
    scanf("%s",digits);
    for(int i=0;digits[i];i++)
    if(digits[i]>'0'||digits[i]>'9'){
        printf("Invalid input");
        return 0;
    }
}