#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define max 25


int top = -1;
char stack[10],stack1[10];

char isOperator(char ch[]){
    return (ch=='+' || ch=='-' || ch=='*' || ch=='/');
}

char isvalid(char ch*){
    return (isalnum(ch) || ch=='+' || ch=='-' || ch=='*' || ch=='/' || ch=='(' || ch==')');
}

char *push(char str[]){
    strcpy(stack[++top],str);
}

char *pop(){
    return stack[top--];
} 

void fun(char str[]){
    int len=strlen(str),chlen;
    char ch;
    for(int i=len-1;i>0;i--){
        ch=str[2];
        temp[0]=ch;
        temp[1]'\0';
        push(temp);
    }
    else if(isvalid(ch)){
        
    }
    else{
        char op1[max], op2[max], res[max]="";
        strcpy(op2,pop());
        strcpy(op1,pop());
        strcpy(res,op2);
        strcat(res,op1);
        chlen=strlen(res);
        res[chlen]=ch;
        res[chlen+1]='\0';
        push(res);
    }
    printf("%s",stack[top]);
}

int main(){
    char str[max];
    scanf("%s",st);
    if(isvaid()){
        
    }
    
}