#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define MAX_SIZE 1000
typedef struct{
    char array[MAX_SIZE];
    int top;
    }charStack;
    void initStack(charStack*stack){
        stack->top=-1;
    }
    void push(charStack*stack,char value)
{
    if(stack->top<MAX_SIZE-1){
        stack->array[++(stack->top)]=value;
    }
}    
char pop(charStack*stack){
    if(stack->top>=0){
        return stack->array[(stack->top)--];
    }
    return '\0';
}
int isEmpty(charStack*stack){
    return stack->top==-1;
}
int isOperator(char c){
    return c =='+' || c == '-' || c=='*' || c=='/' || c=='^';
}
char*prefixToPostfix(const char*expression){
    static char result[MAX_SIZE];
    charStack stack;
    initStack(&stack);
    int j=0;
    for(int i=strlen(expression)-1;i>=0;i--){
        char c=expression[i];
        if(isspace(c)){
            continue;
        }
        if(isalnum(c)){
            push(&stack,c);
        }else if(isOperator(c)){
            if(stack.top<1){
                return "Invalid input";
                
            }
            char op1=pop(&stack);
            char op2=pop(&stack);
            result[j++]=op1;
            result[j++]=op2;
            result[j++]=c;
            push(&stack,result[j-1]);
            }else{
                return "Invalid input";}
            }
            while(!isEmpty(&stack)){
                for(int k=0;k<j/2;k++){
                    char temp=result[k];
                    result[k]=result[j-k-1];
                    result[j-k-1]=temp;
                }
                return result;
            }
            int main(){
                char prefixExpression[MAX_SIZE];
                fgets(prefixExpression,sizeof(prefixExpression),stdin);
                size_t len=strlen(prefixExpression);if(len>0 && prefixExpression[len - 1]=='\n'){
                    prefixExpression[len - 1]='\0';
                }
                char*PostfixExpression=prefixToPostfix(prefixExpression);
                printf("%s\n",PostfixExpression);
                return 0;
            }