Prefix Evaluation-Stacks

#include<iostream>
#include<stack>
#include<math.h>
using namespace std;
int prefixevaluation(string s){
    stack<int> s1;
    for(int i=s.length()-1;i>=0;i--){
        if(s[i]>='0' && s[i]<='9'){
            s1.push(s[i]-'0');
        }
        else
        {
            int op1=s1.top();
            s1.pop();
            int op2=s1.top();
            s1.pop();
            switch(s[i]){
                case '+':
                s1.push(op1+op2);
                break;
                case '-':
                s1.push(op1-op2);
                break;
                case '*':
                s1.push(op1*op2);
                break;
                case '/':
                s1.push(op1/op2);
                break;
                case '^':
                s1.push(op1^op2);
                break;
            }
        }
    }
    return s1.top();
}


int main(){
    cout<<prefixevaluation("*7+52");
    return 0;
}