#include<stdio.h>

void main() {
    int data[10];
    int dataatrec[10],c,c1,c2,c3,i;

    printf("Sender: ");
    scanf("%d %d %d %d",&data[0] ,&data[1] ,&data[2] ,&data[4]);

    //Calculation of even parity
    data[6]=data[0]^data[2]^data[4];
    data[5]=data[0]^data[1]^data[4];
    data[3]=data[0]^data[1]^data[2];

    printf("Encoded Data: ");
    for(i=0;i<7;i++)
        printf("%d",data[i]);

    printf("\nReceiver: ");
    for(i=0;i<7;i++)
        scanf("%d",&dataatrec[i]);

    c1=dataatrec[6]^dataatrec[4]^dataatrec[2]^dataatrec[0];
    c2=dataatrec[5]^dataatrec[4]^dataatrec[1]^dataatrec[0];
    c3=dataatrec[3]^dataatrec[2]^dataatrec[1]^dataatrec[0];
    c=c3*4+c2*2+c1 ;

    printf("\nSyndrome bits:  %d %d %d", c1, c2, c3);

    if(c==0) {
        printf("\nNo error while transmission of data\n");
    }
    else {
        printf("\nError Position: %d",c);

        printf("\nData sent: ");
        for(i=0;i<7;i++)
            printf("%d",data[i]);

        printf("\nData received: ");
        for(i=0;i<7;i++)
            printf("%d",dataatrec[i]);

        printf("\nCorrect message is: ");

        //if errorneous bit is 0 we complement it else vice versa
        if(dataatrec[7-c]==0)
            dataatrec[7-c]=1;
        else
            dataatrec[7-c]=0;

        for (i=0;i<7;i++) {
            printf("%d",dataatrec[i]);
        }
    }
}