[C] Get number of 'a', 'i', 'u', 'e', 'o' in string

//Code programming that I write in Xcode on OSX, some programming tools on Windows will be incompatible.
//Please read instructions on how to edit specific.

#include "stdio.h"
#include "string.h"

int main(void) {
    char cString[31];
    int i, numberOfA = 0, numberOfI = 0, numberOfU = 0, numberOfE = 0, numberOfO = 0;
    printf("Enter string (up to 30): ");
    gets(cString);

    int numberOfElement = (int) strlen(cString) - 1;


    for (i = 0; i < numberOfElement; i++) {
        if (cString[i] == 'i' || cString[i] == 'I') {
            numberOfI++;
        }
    }

    for (i = 0; i < numberOfElement; i++) {
        if (cString[i] == 'a' || cString[i] == 'A') {
            numberOfA++;
        }
    }

    for (i = 0; i < numberOfElement; i++) {
        if (cString[i] == 'u' || cString[i] == 'U') {
            numberOfU++;
        }
    }

    for (i = 0; i < numberOfElement; i++) {
        if (cString[i] == 'e' || cString[i] == 'E') {
            numberOfE++;
        }
    }

    for (i = 0; i < numberOfElement; i++) {
        if (cString[i] == 'o' || cString[i] == 'O') {
            numberOfO++;
        }
    }

    printf("Char(s) have 'A' or 'a': %d\n", numberOfA);
    printf("Char(s) have 'I' or 'i': %d\n", numberOfI);
    printf("Char(s) have 'U' or 'u': %d\n", numberOfU);
    printf("Char(s) have 'E' or 'e': %d\n", numberOfE);
    printf("Char(s) have 'O' or 'o': %d\n", numberOfO);

    return 0;
}