UVa 272 - TEX Quotes, https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=4&page=show_problem&problem=208

uva-272.cpp

#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <list>
#include <algorithm>
#include <string.h>
#include <string>
#include <queue>
#include <stack>
#include <math.h>

int main(void) {
    bool f = false;
    char c;
    
    while(true) {
        int ret = scanf("%c", &c);
        if(ret == EOF) break;
        
        if(c == '"') {
            if(!f) printf("``");
            else printf("''");
            f = !f;
        }else printf("%c", c);
       
    }
    return EXIT_SUCCESS;
}