#include <algorithm>
using namespace std;

#define DIM 100001

struct branza {

    int c, p;
};

int n, s, t, dq[ DIM ];
long long rez;
branza a[ DIM ];

void solve() {

    int i, st, dr;

    scanf( "%d%d%d", &n, &s, &t );
    for( i = 1; i <= n; ++ i )
        scanf( "%d%d", &a[ i ].c, &a[ i ].p );
    st = 1;
    dr = 0;
    for( i = 1; i <= n; ++ i ) {

        for( ; st <= dr && a[ i ].c < a[ dq[ dr ] ].c + ( i - dq[ dr ] ) * s; -- dr );
        dq[ ++ dr ] = i;
        if( i - dq[ st ] > t )
            ++ st;
        rez += ( a[ dq[ st ] ].c + ( i - dq[ st ] ) * s ) * a[ i ].p;
    }
    printf( "%lld", rez );
}

int main() {

    freopen( "branza.in", "r", stdin );
    freopen( "branza.out", "w", stdout );

    solve();

    return 0;
}